* Refactor Wallet import code
The code for wallet import was incredibly messy as it evolved over time from various requests.
This PR:
* splits up each supported format into its own file
* Supports taproot descriptors (through a hack until NBitcoin supports it internally) fixes#5518
* Reduces different paths for handling electrum/non-electrum xpubs
* Allows plugins to add their own import support formats for onchain wallets.
* Update NBitcoin to parse tr descriptors
* Fix warnings
* Use dedicated type OnChainWalletParsers
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Co-authored-by: nicolas.dorier <nicolas.dorier@gmail.com>
