Support Descriptor Wallets for Bitcoin Core

[LiranCohen]

Bitcoin Core has updated its wallet format to use descriptor wallets.
https://github.com/bitcoin/bitcoin/blob/master/doc/descriptors.md

Starting in v23 of core this is now the default for the createwallet rpc:
https://bitcoincore.org/en/releases/23.0/#wallet

Legacy wallets require Berkeley DB to be compiled with the software instead of SQLite for the new descriptor wallets.

Opening this issue as a placeholder for future work for SideTree to support descriptor wallets for bitcoin core.

I'll try to make some time over the next couple of weeks to scope out this change.