Move EventSource to shared CoreLib partition (dotnet/coreclr#23925)

Move EventSource to shared CoreLib partition (dotnet/coreclr#23925)

* Move most of EventSource to shared CoreLib partition

* Reenable some code that can be shared with Microsoft.Diagnostics.Tracing.EventSource.Redist in CoreFX

* Remove unused functions

* Fix placement of #endregion

* Clean up P/Invoke prototypes

* Move remaining code from EventSource_CoreCLR to shared partition (guarded by !CORERT)

* Remove more unnecessary marshalling attributes

* Move remaining CoreRT/ProjectN code to shared partition

* Avoid using Windows errors on non-Windows platforms

Commit migrated from https://github.com/dotnet/coreclr/commit/f7020d98c49d8c89fdad41aae64c018be63c623a