l2geth: add block tag to `eth_estimateGas`

Copies the implementation from upstream
https://github.com/ethereum/go-ethereum/blob/389021a5afd01147c851870c693ded8760e6a08c/internal/ethapi/api.go#L1149

.changeset/brave-garlics-sniff.md

+---
+'@eth-optimism/l2geth': patch
+---
+
+Add the gas estimation block tag to `eth_estimateGas` to be RPC compliant

l2geth/internal/ethapi/api.go

@@ -1062,9 +1062,12 @@ func DoEstimateGas(ctx context.Context, b Backend, args CallArgs, blockNrOrHash
 // EstimateGas returns an estimate of the amount of gas needed to execute the
 // given transaction against the current pending block. This is modified to
 // encode the fee in wei as gas price is always 1
-func (s *PublicBlockChainAPI) EstimateGas(ctx context.Context, args CallArgs) (hexutil.Uint64, error) {
-	blockNrOrHash := rpc.BlockNumberOrHashWithNumber(rpc.PendingBlockNumber)
-	return DoEstimateGas(ctx, s.b, args, blockNrOrHash, s.b.RPCGasCap())
+func (s *PublicBlockChainAPI) EstimateGas(ctx context.Context, args CallArgs, blockNrOrHash *rpc.BlockNumberOrHash) (hexutil.Uint64, error) {
+	bNrOrHash := rpc.BlockNumberOrHashWithNumber(rpc.PendingBlockNumber)
+	if blockNrOrHash != nil {
+		bNrOrHash = *blockNrOrHash
+	}
+	return DoEstimateGas(ctx, s.b, args, bNrOrHash, s.b.RPCGasCap())
 }
 
 // ExecutionResult groups all structured logs emitted by the EVM