Implement QueryResponse

[janaakhterov]

public final class QueryResponse<T> {
    // This field is null-able because not all queries require a payment
    // e.g.  `AccountBalanceQuery` and `TransactionReceiptQuery` 
    // and for those queries the payment is an empty protobuf `Transaction`
    @Nullable
    public final TransactionResponse paymentTransaction;

    // This field will be 0 for free queries
    public final Hbar cost;

    // The ID of the node that returned the response
    public final AccountId nodeId;

    // The response for the query, e.g. `AccountInfo`, `AccountBalance`, `Uint8Array`, `List<TransactionRecord>`
    public final T response;
}

Reason for implementing this type is it doesn't make sense that you can't access the node, cost, or payment transaction itself for a query you've executed. I think it'd benefit users to be able to access this information. This would also allow a user to get the receipt for a payment transaction if that's something they want to do.

Another benefit is extensibility. Having an SDK owned type be returned from all queries would allow us to extend the query responses without breaking changes. Unlike right now where FileContentsQuery, ContractBytecodeQuery, AccountRecordsQuery, and AccountStakersQuery return non-extensible types.