a11y: apply scale to widget extents

At-spi registry can be used to generate pointer events based on ATK's
reported widget size and position.

If the surface is scaled, the reported values need to be scaled with the
same factor otherwise the coordinates won't match.

Closes: GNOME/gtk#1505
2 jobs for issue1505 in 16 minutes and 2 seconds (queued for 1 second)
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passed #164896
build

00:16:02

manual #164897
win32 allowed to fail manual
msys2-mingw32