GTK4 libadwaita issues

This is a list of all known issues seen in the GTK4 + libadwaita port of Dialect:

• Sometimes dimmed widgets get blurred. This includes: text in Search Provider details, disabled PopoverMenu items, toolbar buttons loading state, etc. (https://gitlab.gnome.org/GNOME/gtk/-/issues/3833)
• Textviews' context menu disabled element coloring is wrong. Fixed.

Language Selector-specific Issues

• Keyboard navigation does not highlight items reliably.
• GtkPopover don't have a focus-widget property, so the search entry in a language selector isn't focused by default.
• You cannot press Escape to close the language selector if the search entry is focused.
• You cannot press Return to choose the first language result.

Bugs introduced in later PRs

• AdwCritical errors because of toast queuing issues.
• Styling bug where the "Translate" label is miscolored during the action's transition between enabled and disabled.