This adds a test to expose the failure of #4575 which results in the
selection being incorrect when performing a delete as we are likely
already in a begin_user_action()/end_user_action() pair.
Related #4575
We don't need to apply these here, as it will clear the selection which is
needed for the undo. Otherwise we won't be able to test that we end up at
the right selection afterwards.
We don't want to allow new items to be grouped into a previous action
group after the end_user_action() is called. This ensures that we add a
barrier action in those conditions.
Fixes#4276
