chanfunding: fee estimation based on change output in CoinSelect

Add a dust-limit to `CoinSelect` and let the fee estimation consider if a change output is needed or not, assuring that if the change is below the dust-limit it will go towards the fee instead.

lnwallet/chanfunding/wallet_assembler.go

@@ -289,9 +289,10 @@ func (w *WalletAssembler) ProvisionChannel(r *Request) (Intent, error) {
 		// Otherwise do a normal coin selection where we target a given
 		// funding amount.
 		default:
+			dustLimit := w.cfg.DustLimit
 			localContributionAmt = r.LocalAmt
 			selectedCoins, changeAmt, err = CoinSelect(
-				r.FeeRate, r.LocalAmt, coins,
+				r.FeeRate, r.LocalAmt, dustLimit, coins,
 			)
 			if err != nil {
 				return err