Currently we periodically reap the config.transaction table by deleting the entries whose corresponding sessions are expired.

Here is the code path:

LogicalSessionCacheImpl::_reap ==>_reapSessionsOlderThanFn ==> MongoDSessionCatalog::reapSessionsOlderThan ==>removeExpiredTransactionSessionsFromDisk ==> removeSessionsTransactionRecordsIfExpired ==>
removeSessionsTransactionRecordsFromDisk

The last function deletes the entries form the config.transactions table.

This ticket should keep the current code, but when the feature flag is on (similar to here), additionally delete the entries from the in-memory transaction table.