Implement BlockCache Trait #156

Job	Run time
Bitrot check	1m 31s
Build target wasm32-wasi	14s
Check ZFuture build on Linux	1m 40s
Check ZFuture build on macOS	1m 39s
Check ZFuture build on Windows	4m 55s
Clippy (MSRV)	31s
Latest build on ubuntu-latest	9s
Clippy (beta)	13s
Latest build on windows-latest	11s
Code coverage	3m 27s
Latest build on macOS-latest	9s
Intra-doc links	2m 23s
Rustfmt	14s
protobuf consistency	1m 5s
UUID validity	3s
Test on Linux	1s
Test Orchard on Linux	1s
Test NU6 on Linux	1s
Test on macOS	3m 23s
Test Orchard on macOS	3m 7s
Test on Windows	1s
Test Orchard on Windows	1s
Test NU6 on Windows	1s
	25m 0s

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