Introduce XdgPopupGrab

The XdgPopupGrab is a premade grab filter that makes
it trivial for compositors to implement xdg_popup#grab.
1 job for !166 with work/janet/grab-infrastructure in 7 minutes and 11 seconds (queued for 38 seconds)
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passed linux kf5-qt5 qt5.15 #91722

00:07:11

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