refactor(proto): use derive macro to implement Default for KA #2363

Job	Run time
Verify hyper.h is up to date	40s
Check Style	11s
Check MSRV	26s
Test stable on ubuntu-latest	1m 28s
Test with Miri	47s
features	26s
Test stable on windows-latest	2m 59s
Test C API (FFI)	45s
Test stable on macOS-latest	3m 20s
Test beta on ubuntu-latest	1m 6s
minimal-versions	36s
udeps	25s
Test beta on windows-latest	2m 13s
Test beta on macOS-latest	1m 52s
Test nightly on ubuntu-latest	2m 45s
Test nightly on windows-latest	1m 57s
Test nightly on macOS-latest	2m 52s
Build docs	17s
Check exposed types	16s
CI is green	1s
	25m 22s

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