walletrpc+lnwallet: possibility to define an address type for changes in FundPsbt

By default, P2TR addresses are used for changes. However, some users
might encounter some problems with this change. We add the possibility
to define a custom address type in FundPsbt for default/imported accounts
(only P2TR for now). If no address type is specified for these accounts,
we will use P2WKH by default.

lntest/mock/walletcontroller.go

@@ -212,7 +212,7 @@ func (w *WalletController) ListLeasedOutputs() ([]*base.ListLeasedOutputResult,
 
 // FundPsbt currently does nothing.
 func (w *WalletController) FundPsbt(*psbt.Packet, int32, chainfee.SatPerKWeight,
-	string) (int32, error) {
+	string, *waddrmgr.KeyScope) (int32, error) {
 
 	return 0, nil
 }