Add new image type definitions `ec2` and `ec2-ha` representing the
official RHEL ec2 image types.
Add a `xzArchivePipeline()`, which returns a pipeline producing a XZ
archive from a file produced by a different pipeline.
Add rpmrepo snapshots for `rhui` and `ha` repositories used to generate
image test cases. `rhui` is used by the `ec2` image and it is available
on x86_64 and aarch64 architectures. `ha` is used by the `ec2-ha` image
and it is available only for x86_64.
The new image type definitions are currently not used by any
API test case.
Signed-off-by: Tomas Hozza <thozza@redhat.com>
