feat(ffi): add cargo-c support #2903

Job	Run time
Verify hyper.h is up to date	11s
semver	14s
Check Style	7s
features	30s
Test cargo-c support (FFI)	29s
minimal-versions	25s
Test C API (FFI)	12s
Test with Miri	2m 21s
Check MSRV	16s
udeps	23s
Test stable on ubuntu-latest	1m 2s
Test stable on windows-latest	1m 53s
Test stable on macOS-latest	1m 10s
Test beta on ubuntu-latest	1m 10s
Test beta on windows-latest	1m 58s
Test beta on macOS-latest	1m 13s
Test nightly on ubuntu-latest	1m 6s
Test nightly on windows-latest	2m 1s
Test nightly on macOS-latest	1m 14s
Build docs	18s
Check exposed types	19s
CI is green	0s
	18m 32s

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