Stop acting as admin when the authorization expires

Stop acting as admin when the authorization expires

Previously, the authorization just silently expired without any
visible change. The surprise only came when the user tried to do
any action, which immediately would show a password prompt. We
don't want users to randomly type passwords into password
prompts unexpectedly showing up. This commit avoids that.

With this change, the view container visibly de-escalates
privileges and shows a message explaining what happened.

A method was implemented in kio-admin to make this possible. See:
https://commits.kde.org/kio-admin/a2da29289d12ef845e2c1da17ed04c59f1c47762

This commit also improves some logic around the responsibility
of hiding bars and activating view containers.

This is also part of my project funded by the European Commission.