Avoid boxing in Connector chains #2601

Job	Run time
Test	4s
Test	45s
Test (charset)	33s
Test (charset)	45s
Test (cookies)	14s
build_versions (stable)	44s
cargo-deny (aarch64-apple-ios)	1s
Test (cookies)	45s
Test (socks-proxy)	1s
cargo-deny (aarch64-linux-android)	1s
build_versions (beta)	45s
Test (socks-proxy)	43s
cargo-deny (i686-pc-windows-gnu)	1s
Test (gzip)	13s
build_versions (1.71.1)	45s
Test (gzip)	41s
cargo-deny (i686-pc-windows-msvc)	1s
Test (brotli)	32s
Test (brotli)	44s
cargo-deny (i686-unknown-linux-gnu)	1s
Test (json)	1s
Test (json)	44s
Test (native-tls)	1s
cargo-deny (wasm32-unknown-unknown)	1s
Docs	1s
Test (native-tls)	44s
cargo-deny (x86_64-apple-darwin)	1s
cargo-deny (x86_64-apple-ios)	1s
Lint	1s
cargo-deny (x86_64-pc-windows-gnu)	1s
cargo-deny (x86_64-pc-windows-msvc)	1s
cargo-deny (x86_64-unknown-linux-gnu)	1s
cargo-deny (x86_64-unknown-redox)	1s
	9m 58s

Provide feedback