Add tests for a real-world upgrade scenario to look for breaking changes, and more pipeline cleanup

Depends on !75 (merged) merged

Features:

• Cleans up install/upgrade testing jobs
• Adds a test of a real-world upgrade scenario to look for breaking changes
  • Accomplished by installing the published version of the helm chart from the repo, then upgrading to the chart cloned during the job's initial setup

NOTES:

• At the time of creation, the pipeline fails because chart v1.17.0 is the latest published version.
  • This validates that the test works properly by failing the pipeline because v1.17.0 has a bug which broke installs and upgrades with a pre-configured secret.
  • When v1.17.1 is released, I will re-run the failed job and it is expected to succeed.
  • 1.17.1 has been released and the pipeline succeeded.
• This is marked as draft because of being based on !75 (merged). When that is merged, this will be rebased to reduce the visible changes.

Fixes #39 (closed)