Improve the ETL->ELTX perf by improving the efficiency of GetEventCounts
Improve the ETL->ELTX perf by improving the efficiency of GetEventCounts

The more truely unknown events we have during ETL->ETLX conversion the slower GetEventCounts
is (Because we cant cache the TraceEventCount on an unknown event (because it s shared) like we
can with a known evnet.   Thus force some high volumne events to be known.

vancem/perfview,vancem/perfview,vancem/perfview,vancem/perfview,vancem/perfview