Extend transaction request to support the value of ethereum transaction `data` field directly.

[Chengxuan]

In the current Transaction Manager API, it exposes most of the ethereum transaction fields apart from the input data: https://github.com/hyperledger/firefly-transaction-manager/blob/main/pkg/ffcapi/api.go#L231. the input data is constructed using the method and params inside the transaction manager logic. While this design satisfies the need of Firefly functionality, it creates friction for web3 developers to try out the Transaction Manager API with the raw eth transaction payload.

Therefore, to improve the flexibility of transaction manager, data fields should be added to the existing input transaction fields as an alternative to the existing fields.