Create universal template and label that would accommodate different rhel needed by interop testing team

We would like to use universal label that would cover different rhel versions that are required by interop testing. The idea is that we will keep one/two label for interop testing slave: rhel-interop (and possibly for both stream, so rhel7-interop and rhel8-interop), which would have used image: rhel-interop-7(8)-snapshot that would have actually needed rhel version to test. During provisioning we will replace snapshot with proper rhel. This way we can keep these two labels and do not need to change interop test job label all the time via PR in cci-config repo.

Reqs:

• UMB trigger for interop rhel to run provision job with
• job will be parametrized based on rhel version given by umb message
• jenkins provisioning job build description needs to be updated to have available info about rhel version

Pros:

• do not need to change code via PR every time there is new bits to test
• probably can be fully automated

Cons:

• only one version to test at a time
• complex and possibly unstable?