quirks: sway does not damage surface beneath sub-surface, when unmapped

When unmapping a sub-surface, Sway <= 1.8 does not damage the surface
beneath the sub-surface.

https://github.com/swaywm/sway/issues/6960

The workaround is to manually damage the main surface. Previously,
this was done when exiting scrollback search, and after the ‘flash’
OSC. But other sub-surfaces, that may also be unmapped, did not.

This patch adds a quirk handler that does this, and calls it when:

* Exiting scrollback search
* Ending the ‘flash’ OSC
* Exiting unicode input mode
* Clearing URL labels
* Removing the scrollback position indicator

Closes #1335

url-mode.c

@@ -14,6 +14,7 @@
 #include "char32.h"
 #include "grid.h"
 #include "key-binding.h"
+#include "quirks.h"
 #include "render.h"
 #include "selection.h"
 #include "spawn.h"
@@ -859,6 +860,10 @@ urls_reset(struct terminal *term)
         tll_foreach(term->window->urls, it) {
             wayl_win_subsurface_destroy(&it->item.surf);
             tll_remove(term->window->urls, it);
+
+            /* Work around Sway bug - unmapping a sub-surface does not
+             * damage the underlying surface */
+            quirk_sway_subsurface_unmap(term);
         }
     }