Rework 'file name widget' popover and dialogs
This reworks the file-name-widget-controller mechanism into utility functions and template instantiations.
In the process of unraveling the code paths from the extra abstraction layer, this also ports from the deprecated GtkDialog
to AdwWindow
.
The commit order is somewhat grown naturally. In that some function removals could potentially be combined, but I think in its current shape it's easier to follow the transition from NautilusFileNameWidgetController
inheritance to template instantiation with respective parent widget instance.
Related to #2722
Edited by Peter Eisenmann