Make sure that the view colorset is correct, remove unnecessary layer
(clip is enabled), and remove unnecessary visibility hack for the
notifications widget.
This avoids having to completely load the quicksettings, status bar,
media widget, and notifications list from scratch when the view changes.
We now have a single instance of each component which is reparented to
the new view (portrait/landscape).
Fixes https://invent.kde.org/plasma/plasma-mobile/-/issues/406