new: Support pinning proto in `.prototools`. (#560) #380

Job	Run time
Stable - aarch64-unknown-linux-gnu	10m 23s
Stable - x86_64-unknown-linux-gnu	6m 13s
Stable - x86_64-apple-darwin	12m 24s
Stable - aarch64-apple-darwin	13m 32s
Stable - x86_64-pc-windows-msvc	14m 14s
	56m 46s

Provide feedback