feat(http1): support configurable `max_headers` #2532

Job	Run time
Check Style	11s
semver	13s
Verify hyper.h is up to date	2m 20s
minimal-versions	28s
Test C API (FFI)	41s
Test with Miri	1m 43s
features	40s
Check MSRV	50s
udeps	22s
Test stable on ubuntu-latest	1m 12s
Test stable on windows-latest	2m 52s
Test stable on macOS-latest	2m 15s
Test beta on ubuntu-latest	1m 25s
Test beta on windows-latest	2m 36s
Test beta on macOS-latest	2m 3s
Test nightly on ubuntu-latest	1m 31s
Test nightly on windows-latest	2m 47s
Test nightly on macOS-latest	2m 59s
Build docs	20s
Check exposed types	17s
CI is green	1s
	27m 46s

Provide feedback