make (de)tensorization events measure level events (#4958)
* make tensorizer events measures
* throttle the events and add a new one SoftwareBitmapToGPUTensorTelemetryEvent
* factor out timing code into a class
* typo
* typo
* move eventimer class into its own header file
* add throttling to detensorization and remove variable timing
* make detensorization events measures as well
* add ConvertGPUTensorToSoftwareBitmapTelemetryEvent event
* de-duplicate event names
* fix comment
* PR feedback
