[CI] Add a scheduled workflow for tests and benchmarks (#2822)

# Motivation

We want to run our unit tests, integration tests and benchmarks on a
regular schedule to understand how stable they are.

# Modification

This PR adds a scheduled workflow for the three above jobs. It runs it
three times a day so we get enough data throughout the day.

# Result

Continuous feedback about the stability of our tests.

.github/workflows/pull_request_label.yml

@@ -10,5 +10,7 @@ jobs:
         runs-on: ubuntu-latest
         timeout-minutes: 1
         steps:
+            - name: Checkout repository
+              uses: actions/checkout@v4
             - name: Check for semver label
-              uses: ./github/actions/pull_request_label_checker.yml
+              uses: ".github/actions/pull_request_semver_label_checker/action.yml"

.github/workflows/scheduled.yml

@@ -0,0 +1,29 @@
+name: Scheduled
+
+on:
+    schedule:
+        - cron: "0 8,20 * * *"
+
+jobs:
+    unit-tests:
+        name: Unit tests
+        uses: ./.github/workflows/unit_tests.yml
+        with:
+            linux_5_8_arguments_override: "-Xswiftc -warnings-as-errors --explicit-target-dependency-import-check error"
+            linux_5_9_arguments_override: "-Xswiftc -warnings-as-errors --explicit-target-dependency-import-check error"
+            linux_5_10_arguments_override: "-Xswiftc -warnings-as-errors --explicit-target-dependency-import-check error"
+            linux_nightly_6_0_arguments_override: "--explicit-target-dependency-import-check error"
+            linux_nightly_main_arguments_override: "--explicit-target-dependency-import-check error"
+
+    benchmarks:
+        name: Benchmarks
+        uses: ./.github/workflows/benchmarks.yml
+        with:
+            benchmark_package_path: "Benchmarks"
+
+    integration-tests:
+        name: Integration Tests
+        uses: ./.github/workflows/swift_matrix.yml
+        with:
+          name: "Integration tests"
+          matrix_linux_command: "apt-get update -y -q && apt-get install -y -q lsof dnsutils netcat-openbsd net-tools curl jq && ./scripts/integration_tests.sh"