rpc: configure gas cap (#457)

* rpc: configure gas cap

* c++

* rm old const

* docs

ethereum/rpc/namespaces/eth/api.go

@@ -167,8 +167,7 @@ func (e *PublicAPI) Hashrate() hexutil.Uint64 {
 // GasPrice returns the current gas price based on Ethermint's gas price oracle.
 func (e *PublicAPI) GasPrice() *hexutil.Big {
 	e.logger.Debug("eth_gasPrice")
-	// TODO: use minimum value defined in config instead of default or implement oracle
-	out := big.NewInt(ethermint.DefaultGasPrice)
+	out := new(big.Int).SetUint64(e.backend.RPCGasCap())
 	return (*hexutil.Big)(out)
 }
 
@@ -438,7 +437,7 @@ func (e *PublicAPI) doCall(
 	if err != nil {
 		return nil, err
 	}
-	req := evmtypes.EthCallRequest{Args: bz, GasCap: ethermint.DefaultRPCGasLimit}
+	req := evmtypes.EthCallRequest{Args: bz, GasCap: e.backend.RPCGasCap()}
 
 	// From ContextWithHeight: if the provided height is 0,
 	// it will return an empty context and the gRPC query will use