Move away from tracking presses/releases directly, since there might be
other event handlers on top that might prevent the popup event handler
to fully track all events. The replacement is using event state modifiers,
which will use information set from the backend, and is enough to determine
there's no more pressed buttons without tracking prior event history.
This makes the popup event handler able to interact with other event
handlers that might be on top, and consume button release events for
themselves (e.g. DnD), no longer resulting in a stuck popup grab.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3937>
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