collect the base fee instead of burning it (#5)

EIP-1559 burns the base fee. This doesn't make sense for rollups. The
set fee recipient should collect it.

core/state_transition.go

@@ -467,16 +467,15 @@ func (st *StateTransition) TransitionDb() (*ExecutionResult, error) {
 	if rules.IsLondon {
 		effectiveTip = cmath.BigMin(msg.GasTipCap, new(big.Int).Sub(msg.GasFeeCap, st.evm.Context.BaseFee))
 	}
-	effectiveTipU256, _ := uint256.FromBig(effectiveTip)
 
 	if st.evm.Config.NoBaseFee && msg.GasFeeCap.Sign() == 0 && msg.GasTipCap.Sign() == 0 {
 		// Skip fee payment when NoBaseFee is set and the fee fields
 		// are 0. This avoids a negative effectiveTip being applied to
 		// the coinbase when simulating calls.
 	} else {
-		fee := new(uint256.Int).SetUint64(st.gasUsed())
-		fee.Mul(fee, effectiveTipU256)
-		st.state.AddBalance(st.evm.Context.Coinbase, fee, tracing.BalanceIncreaseRewardTransactionFee)
+		fee := new(big.Int).SetUint64(st.gasUsed())
+		fee.Mul(fee, effectiveTip)
+		st.state.AddBalance(st.evm.Context.Coinbase, uint256.MustFromBig(fee), tracing.BalanceIncreaseRewardTransactionFee)
 
 		// collect base fee instead of burn
 		if rules.IsLondon && st.evm.Context.Coinbase.Cmp(common.Address{}) != 0 {