Ensure raw bytes sent by the user are used for signature verification

[netopyr]

Different Protobuf libraries serialize and deserialize protobuf files inconsistently, as the order of fields is not specified. To ensure that signature verifications succeed for transactions that store the TransactionBody in Transaction.body, we must use the raw bytes provided by the user.

Once access to the raw bytes has been added to PBJ, we have to modify the TransactionChecker.check() to use them instead of serializing the extracted TransactionBody.