[Coop] Convert and cleanup open/create of named mutex/event/semaphore. (#12002)
* [Coop] Convert System.Threading.Semaphore.
Potential handles are avoided through fixed, but error path converting utf16 to utf8 is introduced.
* [Coop] Cleanup System.Threading.Mutex. Replace gchandle pinning with C# fixed.
* Remove two commented out lines that are not likely to materialize.
* [Coop] Cleanup System.Threading.NativeEventCalls. Replace gchandle with C# fixed.
* Don't assume ves_icall_System_Threading_Semaphore_ReleaseSemaphore_internal output is to stack.
15 files changed: