Thread scheduler rewrite (#393)

* Started to rewrite the thread scheduler

* Add a single core-like scheduling mode, enabled by default

* Clear exclusive monitor on context switch

* Add SetThreadActivity, misc fixes

* Implement WaitForAddress and SignalToAddress svcs, misc fixes

* Misc fixes (on SetActivity and Arbiter), other tweaks

* Rebased

* Add missing null check

* Rename multicore key on config, fix UpdatePriorityInheritance

* Make scheduling data MLQs private

* nit: Ordering

Ryujinx.HLE/HOS/Kernel/IKFutureSchedulerObject.cs

@@ -0,0 +1,7 @@
+namespace Ryujinx.HLE.HOS.Kernel
+{
+    interface IKFutureSchedulerObject
+    {
+        void TimeUp();
+    }
+}