Avoid too wide sidebar when writedirection controls are activated

Achieved by placing the nearby controls into the same box.

Change-Id: I28d04c8c3c5b5d9989e30d0ca18ef536640fb87a
Reviewed-on: https://gerrit.libreoffice.org/6609
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>