connection: print array size

This makes it easier to understand how an xdg_toplevel is configured for
instance.

Signed-off-by: Simon Ser <contact@emersion.fr>
2 jobs for print-array in 1 minute and 27 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Build
passed #2869792
build-native-autotools

00:01:27

passed #2869793
build-native-meson

00:00:53