Rewrite scheduler context switch code (#1786)

* Rewrite scheduler context switch code

* Fix race in UnmapIpcRestorePermission

* Fix thread exit issue that could leave the scheduler in a invalid state

* Change context switch method to not wait on guest thread, remove spin wait, use SignalAndWait to pass control

* Remove multi-core setting (it is always on now)

* Re-enable assert

* Remove multicore from default config and schema

* Fix race in KTimeManager

Ryujinx.HLE/HOS/Kernel/Threading/KConditionVariable.cs

@@ -7,7 +7,7 @@ namespace Ryujinx.HLE.HOS.Kernel.Threading
     {
         public static void Wait(KernelContext context, LinkedList<KThread> threadList, object mutex, long timeout)
         {
-            KThread currentThread = context.Scheduler.GetCurrentThread();
+            KThread currentThread = KernelStatic.GetCurrentThread();
 
             context.CriticalSection.Enter();