Port filechooser to GtkColumnView

(Depends on !5098 (merged))

TODO:

• Drop GtkTreeModel implementation of GtkFileSystemModel
• Reintroduce filters to GtkFileSystemModel
• (Optional) Rewrite GtkFileSystemModel using nested list models
• Reimplement context menus
  • Move event controllers to rows
  • Move per-item actions to rows
  • Fix rename popover
• Bring back most of show_and_select_files()
  • Show hidden files if needed
  • Remove filters if needed
• Drag n' drop
• File sorting
• Handle icon theme changes
• Drop tree model use in GtkFileChooserEntry (or drop this widget)
• Bring back filechooser settings save/restore
• Figure out the padding situation for cells