Consider fake SDK sync related components

[HonzaR]

Is your feature request related to a problem? Please describe.

In our tests as well as in the Compose Previews we'd appreciate having a way how to mock our key synchronizer components.

Describe the solution you'd like

It requires mocking a few components like networking client (https://github.com/zcash/zcash-android-wallet-sdk/issues/898), Synchornizer, DerivedDataRepository, CompactBlockProcessor (CompactBlockDownloader & CompactBlockRepository), or TransactionManager.

The rust backend is already mocked as FakeRustBacked.

All of these would be just SDK internal components used for internal testing and similar use-cases.