zcash_client_backend: Generalize & extend wallet metadata query API #6055

Job	Run time
Latest build on ubuntu-latest	2m 10s
Check ZFuture build on Linux	25s
Latest build on windows-latest	6m 51s
Check ZFuture build on macOS	33s
Latest build on macOS-latest	1m 56s
Check ZFuture build on Windows	4m 2s
Bitrot check	1m 30s
Build target wasm32-wasi	57s
Clippy (MSRV)	1m 19s
Clippy (beta)	15s
Code coverage	1h 38m 49s
Intra-doc links	2m 11s
Rustfmt	16s
protobuf consistency	1m 13s
Test on Linux	6m 41s
UUID validity	2s
Test Orchard on Linux	8m 46s
Test NU7 on Linux	6m 43s
Test on macOS	9m 28s
Test Orchard on macOS	10m 25s
Test on Windows	11m 10s
Test Orchard on Windows	16m 48s
Test NU7 on Windows	12m 29s
Required status checks have passed	1s
	3h 25m 0s

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