Make use of Builder::serve_buffered_connection #433

Job	Run time
semver	23s
Check Style	10s
Test with Miri	58s
features	1m 3s
Check MSRV (1.63)	2m 2s
Test stable on ubuntu-latest	38s
Test stable on windows-latest	2m 12s
Test stable on macos-latest	32s
Test beta on ubuntu-latest	39s
Test beta on windows-latest	1m 27s
Test beta on macos-latest	36s
Test nightly on ubuntu-latest	36s
Test nightly on windows-latest	1m 15s
Test nightly on macos-latest	36s
Build docs	13s
CI is green	1s
	13m 21s

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