research: Explore using zebra on disk database as a source of data for `zcash_client_backend`

[oxarbitrage]

An alternative to https://github.com/ZcashFoundation/zebra/issues/8358 will be to make the zcash_client_backend to read and use the data in the Zebra on disk database. A replacement of this kind will make all functionality of the crate to remain working as it is but pulling the data from that source instead.