Avoid boxing in DefaultConnector chain #2611

Job	Run time
Docs	1m 27s
build_versions (stable)	9s
build_versions (beta)	2m 51s
Test	53s
Test (charset)	55s
build_versions (1.71.1)	15s
Test	42s
Test (cookies)	46s
cargo-deny (aarch64-apple-ios)	17s
Test (charset)	42s
Test (socks-proxy)	42s
cargo-deny (aarch64-linux-android)	19s
cargo-deny (i686-pc-windows-gnu)	17s
Test (gzip)	45s
Test (cookies)	34s
Lint	16s
cargo-deny (i686-pc-windows-msvc)	23s
Test (brotli)	43s
Test (socks-proxy)	32s
cargo-deny (i686-unknown-linux-gnu)	22s
Test (json)	46s
Test (gzip)	30s
cargo-deny (wasm32-unknown-unknown)	21s
Test (native-tls)	49s
Test (brotli)	30s
cargo-deny (x86_64-apple-darwin)	16s
Test (json)	31s
cargo-deny (x86_64-apple-ios)	22s
Test (native-tls)	40s
cargo-deny (x86_64-pc-windows-gnu)	22s
cargo-deny (x86_64-pc-windows-msvc)	17s
cargo-deny (x86_64-unknown-linux-gnu)	18s
cargo-deny (x86_64-unknown-redox)	17s
	19m 49s

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