test-cases: Add group to test cases

These groups are set according to the template name in which the test is
referenced.

The group of a test will be used to generate the different test jobs
that can be run with the same template on the same boot, without having
to keep each test name in the templates.

Note that only the automated tests have a group set.

Sanity checks are still hardcoded in templates header.

Signed-off-by: Detlev Casanova <detlev.casanova@collabora.com>