[UI] Add simple support for controller usage in UI

- Disabled unnecessary hotkeys thread when it is not used
- Removed problematic xam_exports static initialization
- Moved xam_dialogs_shown_ and xam_nui_dialogs_shown_ to XamState

src/xenia/kernel/xam/xam_state.h

@@ -59,6 +59,9 @@ class XamState {
 
   X_DASH_APP_INFO dash_app_info_ = {};
 
+  std::atomic<int32_t> xam_dialogs_shown_ = {0};
+  std::atomic<int32_t> xam_nui_dialogs_shown_ = {0};
+
  private:
   KernelState* kernel_state_;