Introduce an rpc to query only confirmed transactions

[zhangsoledad]

Feature Request

The current implementation of the get_transaction rpc retrieves the status of a transaction by querying both the store and the tx-pool. However, in scenarios where there is high-pressure on the network, the tx-pool may become highly contested, causing a significant drop in performance for this rpc.

To address this issue, a new get_confirmed_transaction rpc could be introduced to retrieve information only about confirmed transactions. This would reduce contention and avoid the performance problems associated with querying the tx-pool. This solution would be useful for users who only need to know whether a transaction has been confirmed or not.

[eval-exec]

How about adding a query param only_committed: Bool to get_transaction, return confirmed_transaction only when only_committed is true.