When adding/removing an action to/from the toolbar, the aspect ratio,
audio channel, and subtitle channel menus would disappear from the
parent settings menu.
My understanding is that this happened because nothing was keeping those
menus present (plugged?) when other actions were plugged/unplugged.
This changes it so "Aspect Ratio", "Subtitles", and "Audio Channels"
each are a TDESelectAction that is dynamically filled with items. This
way, each popup menu is still present after other actions being
plugged/unplugged.
Resolves: TDE/codeine#24
Signed-off-by: mio <stigma@disroot.org>