[Local GC] FEATURE_EVENT_TRACE 1/n: Tracking Event State (#15873)

[Local GC] FEATURE_EVENT_TRACE 1/n: Tracking Event State (#15873)

* [Local GC] FEATURE_EVENT_TRACE 1/n: Add infrastructure for keeping event state within the GC and plumbing to communicate event state changes

* Code review feedback: use a load without a barrier in IsEnabled and put debug-only code under TRACE_GC_EVENT_STATE

* Address code review feedback: add EventPipe callback and comments

* Fix the non-FEATURE_PAL build

* Fix an issue where the GC fails to react to ETW callbacks to occur before the GC is initialized (e.g. on startup when an ETW session is already active)

* Simplify callback locking scheme

* Add a separate callback for each EventPipe provider and funnel them all through a common handler

* Fix non-FEATURE_PAL build