test(kuttl): Install cert-manager

[NickLarsenNZ]

Description

Fixes the broken cert-manager tests.

This installs cert-manager if it doesn't look to already be installed.

It handles concurrent runs (as long as the same script is copied), and cleanup (basically mimicking pre/post run tasks, which kuttl can't do). It does so by using finalizers. The last job remaining will be responsible for cleaning up.

[!NOTE] This might seem overkill, but could serve as a pattern if needed in other tests.

Unfortunately the script can't be shared between tests, as it won't end up in the work directory - so it would need to be copy/pasted if needed in other tests.

Testing

I have tested it by making a concurrent test job that finishes sooner than the real test:

./scripts/run-tests --test cert-manager

--- PASS: kuttl (165.82s)
    --- PASS: kuttl/harness (0.00s)
        --- PASS: kuttl/harness/cert-manager-concurrent_openshift-false (34.82s)
        --- PASS: kuttl/harness/cert-manager-tls_openshift-false (165.81s)
PASS

Definition of Done Checklist

• Not all of these items are applicable to all PRs, the author should update this template to only leave the boxes in that are relevant
• Please make sure all these things are done and tick the boxes

# Author
- [x] Integration tests passed (for non trivial changes)

# Reviewer
- [ ] Changelog updated

[NickLarsenNZ]

Still needs tidying up (line lengths, and repeated calls).