a11y: Do not emit window:activate events on temporary grab

When pressing e.g. a window manager shortcut, Xorg would send FocusOut
NotifyGrab then FocusIn NotifyUngrab.  Currently gtk would then send
window:activate/deactivate, which makes the screen reader think that we
have switched to a non-accessible application and came back again, and thus
reannounce the application frame etc. which we don't want when e.g. just
raising volume.

This checks whether the window is really not focused before sending the
window:deactivate event.

Fixes #85
7 jobs for window-activate-grab-4-2 in 33 minutes and 46 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Build
passed gtk #21550

00:07:47

 
  Flatpak
passed flatpak:demo #21705

00:21:13

passed flatpak:widget-factory #21552

00:04:46

canceled flatpak:demo #21704

passed flatpak:demo #21703

00:16:35

failed flatpak:demo #21551

00:01:30

passed flatpak:demo #21556

00:05:05