xdg-shell: damage view when popup is mapped/unmapped
Test plan: spawn an xdg-shell client that has menus with xdg-popups. Resize the window so that it becomes small. Open a menu and then open a submenu so that the submenu si displayed outside the parent toplevel. Close the submenu. There are damage artifacts on master, there shouldn't be any with this PR.
TODO:
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zxdg-shell-v6 -
xdg-shell stable
Fixes #752 (closed)