Refactor ScImpl#getTxRecordByContractID as an AnswerService in terms of HederaContracts

[tinker-michaelj]

Given an injected instance of HederaContracts, the query-answering logic for a valid ANSWER_ONLY version of ContractGetRecords should amount to:

1. Extract the target contract from the query.
2. Obtain a HederaAccount via contracts.get(id), catching any exception.
3. Provide a response from the HederaAccount#records/exception.