Add importprivkeys RPC

[blocktraveler]

Hy there!

Unfortunately, the PRs are locked, so I'm sharing my thoughts this way.

Over the years, people have asked countless times on various platforms how to import private keys (both legacy and Bech32/SegWit) into a Bitcoin Core descriptor wallet. This issue is especially common in Namecoin. I see no reason why importing private keys, a very basic feature, should be restricted to the point that it's impossible for the average user to succeed. That's why I created the Core-Wallet-Migration-Tools in Python.

However, it would be much easier to have an 'importprivkeys' RPC for descriptor wallets (not to be confused with the legacy 'importprivkey' call). Pls check my initial thoughts:

Proposal: Add importprivkeys RPC (helper for WIF → descriptor import)

Thx!
Uwe