list: Tweak logic for excluding Locale/Debug extensions

The man page states that the --all option for the list command includes
runtime extensions (e.g. that end in .Locale or .Debug) and this is the
case. When --all is omitted, we only show such extensions when the thing
they extend is not already in the list. However when you run a command
like "flatpak list --runtime --columns=application,branch", you get a
list that excludes runtime locale extensions but includes app locale
extensions, since the corresponding apps are not in the list despite
presumably being installed. This doesn't seem like the right behavior,
so tweak the logic so that app locale extensions are excluded when --all
is omitted and --runtime is used.

Strictly speaking the "extension-of" information is not guaranteed to be
present in the deploy data (which acquires it from the metadata), but in
practice it seems to be present for all but Sources extensions, and I
think it should be considered required since we are already using it to
implement functionality elsewhere in Flatpak:
https://github.com/flatpak/flatpak/issues/4585

(cherry picked from commit 470b321c63a3a20b43b7d4142ce3038edc87f808)