In the 0.21 rebase we have descriptor wallets. There is some followup work we need to do to make this usable

• publish design doc which adds CT and pegin descriptors
• add musig and slip77 key wrappers (may require libsecp-zkp update)
• do Taproot descriptors (ideally we'd copy Core here, but maybe we're ahead of their schedule as they haven't started)
• update upgradewallet RPC for Elements (also not yet done in Core, we can wait for them)
• Move PAK key management into its own ScriptPubKeyMan or otherwise separate it from ordinary wallet keys