hle: kernel: Allocate a dummy KThread for each host thread, and use it for scheduling.

src/core/hle/kernel/k_thread.cpp

@@ -1034,11 +1034,7 @@ ResultVal<std::shared_ptr<KThread>> KThread::Create(Core::System& system, Thread
 }
 
 KThread* GetCurrentThreadPointer(KernelCore& kernel) {
-    if (!kernel.CurrentScheduler()) {
-        // We are not called from a core thread
-        return {};
-    }
-    return kernel.CurrentScheduler()->GetCurrentThread();
+    return kernel.GetCurrentEmuThread();
 }
 
 KThread& GetCurrentThread(KernelCore& kernel) {