Add CI workflow to check no_std builds for `pczt` and `zcash_keys` #6308

Job	Run time
Test no-Orchard on Linux	4m 53s
Check ZFuture build on Linux	21s
Slow Test Orchard on Linux	4m 14s
Test Orchard on Linux	6m 45s
Check ZFuture build on macOS	32s
Test no-Orchard on macOS	6m 49s
Slow Test NU7 on Linux	4m 26s
Test NU7 on Linux	6m 49s
Check ZFuture build on Windows	1m 39s
Test Orchard on macOS	8m 37s
Test no-Orchard on Windows	8m 21s
Bitrot check	1m 36s
Test Orchard on Windows	13m 27s
Latest build on ubuntu-latest	2m 3s
Build target wasm32-wasi	58s
Test NU7 on Windows	14m 0s
Latest build on windows-latest	4m 47s
Build target thumbv7em-none-eabihf	36s
Latest build on macOS-latest	1m 58s
Clippy (MSRV)	1m 24s
Clippy (beta)	15s
Code coverage	1h 32m 27s
Intra-doc links	2m 16s
Rustfmt	14s
protobuf consistency	1m 9s
UUID validity	3s
Required status checks have passed	1s
	3h 10m 40s

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