[meta] Add option to FORCE X11 as Graphics Backend (#2820)

* save the option on a external file because settings
  are loaded AFTER Qt window is created and then
  the graphics backend is already applied

Signed-off-by: Caio Oliveira <caiooliveirafarias0@gmail.com>

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/2820
Reviewed-by: MaranBr <maranbr@eden-emu.dev>
Reviewed-by: Shinmegumi <shinmegumi@eden-emu.dev>
Co-authored-by: Caio Oliveira <caiooliveirafarias0@gmail.com>
Co-committed-by: Caio Oliveira <caiooliveirafarias0@gmail.com>

src/qt_common/gui_settings.h

@@ -0,0 +1,15 @@
+// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#pragma once
+
+#include <QSettings>
+#include <QString>
+
+namespace GraphicsBackend {
+
+QString GuiConfigPath();
+void SetForceX11(bool state);
+bool GetForceX11();
+
+} // namespace GraphicsBackend