Implement Cursor Locking and new input focus checks for it

Source/Core/DolphinNoGUI/MainNoGUI.cpp

@@ -98,6 +98,12 @@ bool Host_RendererHasFocus()
   return s_platform->IsWindowFocused();
 }
 
+bool Host_RendererHasFullFocus()
+{
+  // Mouse capturing isn't implemented
+  return Host_RendererHasFocus();
+}
+
 bool Host_RendererIsFullscreen()
 {
   return s_platform->IsWindowFullscreen();

Source/Core/DolphinNoGUI/Platform.h

@@ -51,6 +51,6 @@ protected:
   Common::Flag m_shutdown_requested{false};
   Common::Flag m_tried_graceful_shutdown{false};
 
-  bool m_window_focus = true;
+  bool m_window_focus = true;  // Should be made atomic if actually implemented
   bool m_window_fullscreen = false;
 };