Preparatory refactoring for zcash/librustzcash#1673 #6355

Job	Run time
Build target wasm32-wasi	52s
Check ZFuture build on Linux	29s
Check ZFuture build on macOS	30s
Check ZFuture build on Windows	2m 2s
Test no-Orchard on Linux	4m 37s
Test Orchard on Linux	6m 49s
Test NU7 on Linux	6m 35s
Slow Test Orchard on Linux	4m 25s
Test no-Orchard on macOS	6m 14s
Slow Test NU7 on Linux	4m 24s
Bitrot check	1m 37s
Test Orchard on macOS	9m 36s
Test no-Orchard on Windows	9m 8s
Test Orchard on Windows	12m 27s
Build target thumbv7em-none-eabihf	33s
Test NU7 on Windows	13m 52s
Latest build on ubuntu-latest	2m 7s
Clippy (MSRV)	1m 19s
Clippy (beta)	12s
Latest build on windows-latest	5m 36s
Latest build on macOS-latest	1m 47s
Code coverage	1h 25m 15s
Intra-doc links	2m 14s
Rustfmt	13s
protobuf consistency	1m 5s
UUID validity	6s
Required status checks have passed	1s
	3h 4m 5s

Provide feedback