Add allocation counter tests for isolated EL operations

Motivation:

As with the ELF operations before them, the isolated EL operations currently
incur overhead above-and-beyond the overhead of their non-isolated counterparts.
That's not what we want to see. However, before we "fix" them, we need to add
regression testing to confirm our fix actually worked.

Modifications:

- Add isolated variations of all current EL scheduling tests.
- Where isolated methods didn't have alloc counter tests, add new ones
    for the non-isolated versions too.

Result:

More tests.

IntegrationTests/tests_04_performance/test_01_resources/test_assume_isolated_scheduling_10000_executions.swift

@@ -0,0 +1,34 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftNIO open source project
+//
+// Copyright (c) 2017-2025 Apple Inc. and the SwiftNIO project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftNIO project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+import Dispatch
+import NIOPosix
+
+func run(identifier: String) {
+    measure(identifier: identifier) {
+        let group = MultiThreadedEventLoopGroup(numberOfThreads: 1)
+        let loop = group.next()
+        let dg = DispatchGroup()
+
+        try! loop.submit {
+            for _ in 0..<10_000 {
+                dg.enter()
+                loop.assumeIsolated().execute { dg.leave() }
+            }
+        }.wait()
+        dg.wait()
+        try! group.syncShutdownGracefully()
+        return 10_000
+    }
+}

IntegrationTests/tests_04_performance/test_01_resources/test_flat_schedule_10000_tasks.swift

@@ -0,0 +1,41 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftNIO open source project
+//
+// Copyright (c) 2019-2025 Apple Inc. and the SwiftNIO project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftNIO project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+import Dispatch
+import NIOCore
+import NIOPosix
+
+func run(identifier: String) {
+    measure(identifier: identifier) {
+        let group = MultiThreadedEventLoopGroup(numberOfThreads: 1)
+        let loop = group.next()
+        let counter = try! loop.submit { () -> Int in
+            var counter: Int = 0
+
+            let deadline = NIODeadline.now() + .hours(1)
+
+            for _ in 0..<10000 {
+                loop.flatScheduleTask(deadline: deadline) {
+                    counter &+= 1
+                    return loop.makeSucceededFuture(counter)
+                }
+            }
+
+            return counter
+        }.wait()
+
+        try! group.syncShutdownGracefully()
+        return counter
+    }
+}

IntegrationTests/tests_04_performance/test_01_resources/test_flat_schedule_assume_isolated_10000_tasks.swift

@@ -0,0 +1,41 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftNIO open source project
+//
+// Copyright (c) 2019-2025 Apple Inc. and the SwiftNIO project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftNIO project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+import Dispatch
+import NIOCore
+import NIOPosix
+
+func run(identifier: String) {
+    measure(identifier: identifier) {
+        let group = MultiThreadedEventLoopGroup(numberOfThreads: 1)
+        let loop = group.next()
+        let counter = try! loop.submit { () -> Int in
+            var counter: Int = 0
+
+            let deadline = NIODeadline.now() + .hours(1)
+
+            for _ in 0..<10000 {
+                loop.assumeIsolated().flatScheduleTask(deadline: deadline) {
+                    counter &+= 1
+                    return loop.makeSucceededFuture(counter)
+                }
+            }
+
+            return counter
+        }.wait()
+
+        try! group.syncShutdownGracefully()
+        return counter
+    }
+}

IntegrationTests/tests_04_performance/test_01_resources/test_schedule_assume_isolated_10000_tasks.swift

@@ -0,0 +1,37 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftNIO open source project
+//
+// Copyright (c) 2019-2025 Apple Inc. and the SwiftNIO project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftNIO project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+import Dispatch
+import NIOPosix
+
+func run(identifier: String) {
+    measure(identifier: identifier) {
+        let group = MultiThreadedEventLoopGroup(numberOfThreads: 1)
+        let loop = group.next()
+        let counter = try! loop.submit { () -> Int in
+            var counter: Int = 0
+
+            for _ in 0..<10000 {
+                loop.assumeIsolated().scheduleTask(in: .hours(1)) {
+                    counter &+= 1
+                }
+            }
+
+            return counter
+        }.wait()
+
+        try! group.syncShutdownGracefully()
+        return counter
+    }
+}

IntegrationTests/tests_04_performance/test_01_resources/test_schedule_with_deadline_10000_tasks.swift

@@ -0,0 +1,40 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftNIO open source project
+//
+// Copyright (c) 2019-2025 Apple Inc. and the SwiftNIO project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftNIO project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+import Dispatch
+import NIOCore
+import NIOPosix
+
+func run(identifier: String) {
+    measure(identifier: identifier) {
+        let group = MultiThreadedEventLoopGroup(numberOfThreads: 1)
+        let loop = group.next()
+        let counter = try! loop.submit { () -> Int in
+            var counter: Int = 0
+
+            let deadline = NIODeadline.now() + .hours(1)
+
+            for _ in 0..<10000 {
+                loop.scheduleTask(deadline: deadline) {
+                    counter &+= 1
+                }
+            }
+
+            return counter
+        }.wait()
+
+        try! group.syncShutdownGracefully()
+        return counter
+    }
+}

IntegrationTests/tests_04_performance/test_01_resources/test_schedule_with_deadline_assume_isolated_10000_tasks.swift

@@ -0,0 +1,41 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftNIO open source project
+//
+// Copyright (c) 2019-2025 Apple Inc. and the SwiftNIO project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftNIO project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+import Dispatch
+import NIOCore
+import NIOPosix
+
+func run(identifier: String) {
+    measure(identifier: identifier) {
+        let group = MultiThreadedEventLoopGroup(numberOfThreads: 1)
+        let loop = group.next()
+        let counter = try! loop.submit { () -> Int in
+            var counter: Int = 0
+
+            let deadline = NIODeadline.now() + .hours(1)
+
+            for _ in 0..<10000 {
+                loop.assumeIsolated().scheduleTask(deadline: deadline) {
+                    counter &+= 1
+                    return counter
+                }
+            }
+
+            return counter
+        }.wait()
+
+        try! group.syncShutdownGracefully()
+        return counter
+    }
+}

IntegrationTests/tests_04_performance/test_01_resources/test_submit_10000_tasks.swift

@@ -0,0 +1,38 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftNIO open source project
+//
+// Copyright (c) 2019-2025 Apple Inc. and the SwiftNIO project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftNIO project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+import Dispatch
+import NIOPosix
+
+func run(identifier: String) {
+    measure(identifier: identifier) {
+        let group = MultiThreadedEventLoopGroup(numberOfThreads: 1)
+        let loop = group.next()
+        let counter = try! loop.submit { () -> Int in
+            var counter: Int = 0
+
+            for _ in 0..<10000 {
+                _ = loop.submit {
+                    counter &+= 1
+                    return counter
+                }
+            }
+
+            return counter
+        }.wait()
+
+        try! group.syncShutdownGracefully()
+        return counter
+    }
+}

IntegrationTests/tests_04_performance/test_01_resources/test_submit_assume_isolated_10000_tasks.swift

@@ -0,0 +1,38 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftNIO open source project
+//
+// Copyright (c) 2019-2025 Apple Inc. and the SwiftNIO project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftNIO project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+import Dispatch
+import NIOPosix
+
+func run(identifier: String) {
+    measure(identifier: identifier) {
+        let group = MultiThreadedEventLoopGroup(numberOfThreads: 1)
+        let loop = group.next()
+        let counter = try! loop.submit { () -> Int in
+            var counter: Int = 0
+
+            for _ in 0..<10000 {
+                _ = loop.assumeIsolated().submit {
+                    counter &+= 1
+                    return counter
+                }
+            }
+
+            return counter
+        }.wait()
+
+        try! group.syncShutdownGracefully()
+        return counter
+    }
+}