Add range-based note commitment trees to the light client

[str4d]

Once zcash/incrementalmerkletree#48 is complete, we want to integrate it into zcash_client_backend and zcash_client_sqlite as a component of DAGSync. As a stepping stone towards this, we should integrate it into the zcash_client_sqlite datastore, and then when new notes are discovered as part of scan_cached_blocks, we add them to the new tree. The new tree can then be updated independently of both the existing witnesses and subsequent scan_cached_blocks calls (and perhaps we even leave the existing witness update logic in place initially for minimal disruption).

[nuttycom]

Closed by #831