tests: remove useless legacy tests

All of these 'tests' cover UMS functionality which is neither being
worked on or actively maintained.

The only cases where developers touch UMS code is to unwrap it from the
KMS codepaths and ensure that those are secure.

Anyone who feels strong about having these around can revive them, but
in all honestly do consider _seriously_ what you're doing ;-)

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>