wallet: Replace nFeeRateNeeded with effective_fee

Make sure that all fee calculations use the same feerate.
coin_selection_params.effective_fee is the variable we use for all fee
calculations, so get rid of remaining nFeeRateNeeded usages and just
directly set coin_selection_params.effective_fee.

Does not change behavior.

Github-Pull: #21083
Rebased-From: e2f429e6bb

src/wallet/wallet.cpp

@@ -2814,11 +2814,11 @@ bool CWallet::CreateTransactionInternal(
             CFeeRate discard_rate = GetDiscardRate(*this);
 
             // Get the fee rate to use effective values in coin selection
-            CFeeRate nFeeRateNeeded = GetMinimumFeeRate(*this, coin_control, &feeCalc);
+            coin_selection_params.effective_fee = GetMinimumFeeRate(*this, coin_control, &feeCalc);
             // Do not, ever, assume that it's fine to change the fee rate if the user has explicitly
             // provided one
-            if (coin_control.m_feerate && nFeeRateNeeded > *coin_control.m_feerate) {
-                error = strprintf(_("Fee rate (%s) is lower than the minimum fee rate setting (%s)"), coin_control.m_feerate->ToString(FeeEstimateMode::SAT_VB), nFeeRateNeeded.ToString(FeeEstimateMode::SAT_VB));
+            if (coin_control.m_feerate && coin_selection_params.effective_fee > *coin_control.m_feerate) {
+                error = strprintf(_("Fee rate (%s) is lower than the minimum fee rate setting (%s)"), coin_control.m_feerate->ToString(FeeEstimateMode::SAT_VB), coin_selection_params.effective_fee.ToString(FeeEstimateMode::SAT_VB));
                 return false;
             }
             if (feeCalc.reason == FeeReason::FALLBACK && !m_allow_fallback_fee) {
@@ -2900,7 +2900,6 @@ bool CWallet::CreateTransactionInternal(
                     } else {
                         coin_selection_params.change_spend_size = (size_t)change_spend_size;
                     }
-                    coin_selection_params.effective_fee = nFeeRateNeeded;
                     if (!SelectCoins(vAvailableCoins, nValueToSelect, setCoins, nValueIn, coin_control, coin_selection_params, bnb_used))
                     {
                         // If BnB was used, it was the first pass. No longer the first pass and continue loop with knapsack.