Show cluster used for particular deployment

Problem to solve

Group clusters now make it harder for a user to know which cluster was deployed to.

Further details

This is a general issue - see also https://gitlab.com/gitlab-org/gitlab-ce/issues/55094

Proposal

Show the cluster deployed to in the CI job page. For example:

What does success look like, and how can we measure that?

(If no way to measure success, link to an issue that will implement a way to measure this)

Links / references