feat(ffi): add cargo-c support #2899

Job	Run time
Verify hyper.h is up to date	27s
semver	12s
Check Style	4s
Check MSRV	30s
Test stable on ubuntu-latest	1m 16s
Test stable on windows-latest	3m 8s
Test stable on macOS-latest	1m 22s
Test beta on ubuntu-latest	1m 14s
Test C API (FFI)	22s
features	41s
Test cargo-c support (FFI)	30s
Test beta on windows-latest	2m 13s
Test beta on macOS-latest	1m 19s
minimal-versions	39s
udeps	29s
Test with Miri	2m 38s
Test nightly on ubuntu-latest	1m 15s
Test nightly on windows-latest	2m 7s
Test nightly on macOS-latest	1m 33s
Check exposed types	23s
Build docs	19s
CI is green	0s
	22m 41s

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