Core: Support asynchronously executing functions on the CPU thread

The CPU thread will be interrupted to execute the callback, and then
restored to its old state after execution completes.

Source/Core/Core/Core.h

@@ -82,6 +82,10 @@ void UpdateTitle();
 // This should only be called from the CPU thread or the host thread.
 void RunAsCPUThread(std::function<void()> function);
 
+// Run a function on the CPU thread, asynchronously.
+// This is only valid to call from the host thread, since it uses PauseAndLock() internally.
+void RunOnCPUThread(std::function<void()> function, bool wait_for_completion);
+
 // for calling back into UI code without introducing a dependency on it in core
 using StateChangedCallbackFunc = std::function<void(Core::State)>;
 void SetOnStateChangedCallback(StateChangedCallbackFunc callback);