The switch for enabling/disabling extensions currently bases its
state on the extension's ACTIVE state.
This is problematic in the enabled-but-inactive case, because
activating the switch tries to change the state from off to on,
which leads to enabling an already enabled extension (an obvious
no-op).
The new `enabled` property allows us to do better, and use delayed
state changes where the switch position represents the `enabled`
state, and the trough color whether the extension is ACTIVE.
https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/7004
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/3073>
Manually adding and removing rows to dynamic lists is rather
old-fashioned, GTK 4 strongly encourages the use of models.
Modernize the code by exposing extensions as ListModel, and
bind it to the two lists with appropriate filters.
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/3067>