[l10n]Updated Turkish translation
system: Use the system instance for displaying notifications
system: When the notification daemon is dead get over it
system: Fix debug statement
system: Remove System._listToString
system: A bit more Pythony
Get rid of assert False
dogtail tests: Use the filechooser's path togglebutton instead of the "/" key

This removes a trick where we simply typed the "/" character to force open
the path entry in GTK filechooser. We now check the path togglebutton's state
and click it if needed. This approach is potentially safer.

While theoretically slower, the actual performance impact is mostly negligible:
for example, the medialibrary test takes 20.8 seconds instead of 20.7.
dogtail tests: Add some sleeps to prevent false alarms on some tests
Update the app icon

- part of the gnome goal:
  https://wiki.gnome.org/GnomeGoals/HighResolutionAppIcons

https://bugzilla.gnome.org/show_bug.cgi?id=711382
bin/pitivi.in : Don't call GObject.threads_init if pygobject is recent enough.
widgets: Remove "PresetChoiceWidget" as it is not used anywhere.
widgets: remove ResolutionWidget as grep shows it is unused.
All around: fix positional arguments warnings

They appeared with pygobject 3.11.
Hope none flied under the radar.
medialibrary: Correctly represent imported vs total clips in the progressbar
medialibrary.ui: Use a smaller, symbolic label for warning_infobar close button

The use of the "Close" label made the button a bit too prominent, especially
in languages such as French. Besides, one can argue that the verb "close"
may be weird in the context of an infobar inside another widget.
Using the "✖" unicode symbol and a tooltip instead.
medialibrary: Show the amount of errors with ngettext in warning_infobar

Until now we just said "Errors occurred while importing", so we might as well
say the exact number to let the user know how many clips failed to import.

This is also demonstrates Python's new standard way of formatting strings.
Update French translation and improve the French AppData.xml description
Updated Polish translation
Updated Slovenian translation