[Base] Moved IsUseNexusForGameBarEnabled from emulator_window to system.h

This will remove direct usage of system specific code from emulator_window

src/xenia/app/emulator_window.cc

@@ -1870,24 +1870,6 @@ void EmulatorWindow::ToggleGPUSetting(gpu_cvar value) {
   }
 }
 
-// Determine if the Xbox Gamebar is enabled via the Windows registry
-bool EmulatorWindow::IsUseNexusForGameBarEnabled() {
-#ifdef _WIN32
-  const LPCWSTR reg_path = L"SOFTWARE\\Microsoft\\GameBar";
-  const LPCWSTR key = L"UseNexusForGameBarEnabled";
-
-  DWORD value = 0;
-  DWORD dataSize = sizeof(value);
-
-  RegGetValue(HKEY_CURRENT_USER, reg_path, key, RRF_RT_DWORD, nullptr, &value,
-              &dataSize);
-
-  return (bool)value;
-#else
-  return false;
-#endif
-}
-
 void EmulatorWindow::DisplayHotKeysConfig() {
   std::string msg = "";
   std::string msg_passthru = "";

src/xenia/app/emulator_window.h

@@ -236,7 +236,6 @@ class EmulatorWindow {
                          bool vibrate = true);
   void GamepadHotKeys();
   void ToggleGPUSetting(gpu_cvar index);
-  bool IsUseNexusForGameBarEnabled();
   void DisplayHotKeysConfig();
 
   static std::string CanonicalizeFileExtension(