Implement eth_sendRawTransaction for large Ethereum TXns

[Kalina-Todorova]

Economics should be cleared out
Depends on services implementation

[Daniel-K-Ivanov]

Problem
eth_sendRawTransaction assumes that the provided Ethereum transaction is lower than 6KB, thus it directly uses the new EthereumTransaction().setEthereumData(transactionBuffer) functionality from the Hedera JS SDK.

If a user wants to submit a transaction > 6kb (contract deployment), the submission will fail.

Short term Solution
Change the implementation of the relay such that, if the transaction submitted is >= 4KB (we need a buffer for the relay signature), a new flow is executed, which uploads the data of the transaction with the following algorithm:

1. Cut the data property from the encoded transaction
2. Upload the first 4kb of the data property using FileCreate
3. If the data property is >=4kb, execute n number of FileAppends where n is Math.ceil(TransactionBytes - 4kb)
4. Populate the callData property of the EthereumTransaction with the ID of the created File
5. Submit the Ethereum transaction without the data property

Details on how to utilise the File ID for passing data in the transaction payload can be found here:
https://hips.hedera.com/hip/hip-410

[Nana-EC]

We should be able to simplify the logic since SDK intend to implement this.

In which case we are just left with the economics of it

[natanasow]

Blocked, because we need this fix to be merged/released.