Presently operations against the oplog (eg Change Streams) increment various serverStatus metrics such as queryExecutor.scannedObjects and document.returned. We should separate out reporting of this work into its own metric so that downstream consumers can better attribute the sources. Bonus points if we can further differentiate between internal and external callers for the oplog operations.

Note: if queryExecutor.scanned or other metrics are also incremented by these operations then those should be included in this change as well.