This commit changes the metadata viewer to use `GtkListBox`es instead of
`GtkTreeView`s for displaying the tags and their values. The main
advantages is that the latter isn't available in GTK4 (making the
eventual port to it smaller), that they have a11y problems, and that
list boxes allow more advanced UIs than just showing a simple string.
One thing for example that this commit introduces, is to make the labels
selectable, so they can be easily copy-pasted for lookup.
Since we wanted to use `GListModel`, this commit also introduces a
helper object `GimpMetadataTagObject` which holds both a tag's name and
its value. In the future, we could use this to move the string
formatting logic to that helper object, which we could then in turn use
for more advanced UIs.
plug-ins: Use G_DECLARE_FINAL_TYPE in metadata plugin
Use the opportunity also to rename the plug-in to a more
self-explanatory `GimpMetadataViewer` (rather than a `Metadata` struct
which can be easily confused with `GimpMetadata`).
* Since the appimage is for testing purposes, let's use system 'libc'
* Hardcode python path since the wildcard wasn't expanding misteriously
* Improve system theme recognition making way simpler
gitlab: Add url to the Duplicate candidate report search for both open and closed reports.
This may help to reduce the number of duplicate reports we get about some (temporarily) frequently reported issues, like the current crash
happening since GLib 2.79/2.80, or the crash happening with older GIMP versions on macOS Sonoma.
This won't be perfect because not everyone will use or read the template, or notice the url in it, or use the url to find and check the
reports, but I count on it getting more known than right now.
