SERVER-103180 changed the Cursor interface to require explicit RecoveryUnit for every API. However, at the wiredtiger level the WT_SESSION associated with a WT_CURSOR is not free to change, sessions are owned by RUs so it made sense that a (server-level) cursor would fix its RU, that RU would outlive the cursor it opened and all cursor API calls would re-use it. The RecordCursor interface currently does that, and we should change the SortedDataInterface::Cursor interface to make it consistent.