internal/ethapi: add optional parameter blockNrOrHash to estimateGas (e…

…thereum#21545)

This allows users to estimate gas on top of arbitrary blocks as well as pending and latest.
Tracing on pending is useful for most users as it takes into account the current txpool while
tracing on latest might be useful for users that have little to know knowledge of the current
transactions in the network.

If blockNrOrHash is not specified, estimateGas defaults to pending

internal/ethapi/api.go

@@ -1051,9 +1051,12 @@ 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.
-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