Instead of iterating action groups manually,
just show what the action muxer provides. This
gives an accurate view of what actions are
available in a widgets context, and saves us
the trouble of juggling prefixes manually.
We were hardcoding that GtkApplicationWindow only
has a single action group with prefix 'win', but
that is no longer the case. Simply use the code
for the general widget case that can handle multiple
action groups.
The hand-rolled stack combo we were using before
was looking at the visibility of the page itself
to show or hide items. Other stack switchers
expect us to use the GtkStackPage::visible
property for this.
The sidebar in the object page was using up more space than it deserves.
Replace it with a combo box in the subheader. Now that we have more space,
put the CSS node tree and the style properties in the same page again.
These functions, while added for use by the GTK inspector, are generally
useful to applications that need to resolve what action groups are
available to a particular GtkWidget.
https://bugzilla.gnome.org/show_bug.cgi?id=741386
The entire UI is constructed with templates, so the wrapper
constructors are never called, except for gtk_inspector_window_new,
which gets called from the GTK+ code.
Show the actions that are added to GtkApplication and
GtkApplicationWindows, as well as action groups that are
inserted elsewhere with gtk_widget_insert_action_group.
https://bugzilla.gnome.org/show_bug.cgi?id=730095
