Use image_type_tags in repo definitions used for generating image test
cases. Enhance the `generate-test-cases` script to take the
image_type_tags into account when creating a compose request for a
specific image test case.
The motivation for the change is to keep the list of repositories in the
compose request of a image test case as small as possible. Previously,
all of the defined repositories were part of each image test cases for a
specific architecture, even those that were not needed.
Regenerate affected image test cases.
Signed-off-by: Tomas Hozza <thozza@redhat.com>