research: Explore populating in memory wallet from zebra

[oxarbitrage]

In https://github.com/zcash/librustzcash/pull/1293 a memory wallet is introduced into the zcash_client_backend crate.

Inside there are structs like MemoryWalletDb that will need to be populated with Zebra data.

This ticket is to explore that possibility, check if it is doable and end up with a proof of concept if possible to work forward.