view: remove server->last_raised_view

We were skipping in view_move_to_front() if the raised view is already
cached as server->last_raised_view. But this was prone to bugs that
windows cannot be raised even though they are actually not placed at the
top in the scene.

This happened when a window is mapped but view_move_to_front() is not
called in view_impl_map() for some reason. Example cases were:
- a window is minimized before being mapped (#2627)
- a window is mapped while window switcher is active (#2629)

Also, this problem was the root cause of #1640 and #2582, though they are
already fixed.

Therefore, this commit removes server->last_raised_view. In order to
eliminate unnecessary communications between labwc and xwayland (ref:
db591d1), I'll introduce another caching mechanism in the next commit.

include/labwc.h

@@ -292,11 +292,6 @@ struct server {
 	 * Note that active_view is synced with foreign-toplevel clients.
 	 */
 	struct view *active_view;
-	/*
-	 * Most recently raised view. Used to avoid unnecessarily
-	 * raising the same view over and over.
-	 */
-	struct view *last_raised_view;
 
 	struct ssd_hover_state *ssd_hover_state;