We want the currentOp entry for both active and inactive transactions to contain an entry with a transaction.parameters sub document that contains the readConcern and the readTimestamp of the transaction. The readConcern we output here should be the readConcern after any potential upconvert, which should be stored in ReadConcernArgs::_level. The read timestamp should be stored on the session.

For active transactions, the CurOp::reportCurrentOpForClient method should attach this information to the appropriate sub-document, and for inactive transactions, the Session::reportStashedState method should attach it.