video: Don't minimize fullscreen windows on focus loss by default when mode switching is disabled

When mode switching is disabled in a video backend, fullscreen windows are basically just fullscreen desktop windows with different internal scaling.  As no mode switching occurs, there's no need to minimize them on focus loss by default.  This can still be overridden by explicitly setting the internal hint for minimizing on focus loss.

This has the side effect of fixing a bug on GNOME, where, when a fullscreen Wayland window has it's focus lost and restored via alt+tab followed by switching back to windowed mode, the top portion of the window won't end up being obstructed by GNOME's top bar.

src/video/SDL_video.c

@@ -3060,7 +3060,8 @@ ShouldMinimizeOnFocusLoss(SDL_Window * window)
     /* Real fullscreen windows should minimize on focus loss so the desktop video mode is restored */
     hint = SDL_GetHint(SDL_HINT_VIDEO_MINIMIZE_ON_FOCUS_LOSS);
     if (!hint || !*hint || SDL_strcasecmp(hint, "auto") == 0) {
-        if ((window->flags & SDL_WINDOW_FULLSCREEN_DESKTOP) == SDL_WINDOW_FULLSCREEN_DESKTOP) {
+        if ((window->flags & SDL_WINDOW_FULLSCREEN_DESKTOP) == SDL_WINDOW_FULLSCREEN_DESKTOP ||
+            _this->disable_display_mode_switching == SDL_TRUE) {
             return SDL_FALSE;
         } else {
             return SDL_TRUE;