cullable: Take geometry scale into account

Similar like how we scale the opaque region by the geometry scale,
we need to take it into account when checking the size of the actor.

This enables culling of scaled actors with non-fractional scaling.

GNOME/mutter!712
5 jobs for !712 with cull-transformed-actors in 6 minutes and 49 seconds (queued for 2 seconds)
latest detached
Status Job ID Name Coverage
  Review
passed #450785
check-commit-log

00:00:22

 
  Build
passed #450786
build-mutter

00:03:06

passed #450787
build-without-native-backend

00:02:54

 
  Test
passed #450789
can-build-gnome-shell

00:01:59

passed #450788
test-mutter

00:03:19