QA infra test improvements

[MichaelThamm]

For context, first read this HowTo:

• https://github.com/canonical/observability-team/blob/main/how-to/test-products-with-solqa.md

We should improve our QA tests so we have a maintainable implementation and better coverage. This can be done in a few ways:

• Add pytests to our sqa folder under tests, and any other helper functions there. These are executed by the sqa_tests in the root repo.
• We should try to avoid having a test variant per product flavor: COS / COS Lite. The main differences are otelcol and timeouts
  • We likely don't want to wait 2h for active/idle for COS Lite, although this is valid for COS.
  • Consider a good design for checking which flavor we have and piping that into each helper script.
• We should choose which tests we already have in tests/solution and port them over to tests/sqa, or better yet, make them reusable?
• We should output our results in xUnit format, like how the Juju team does it. They do it in GoLang, but we can do it in some Pythonic way.
  • This will get rid of this warning
• We could also address this warning by generating a metrics.json file (likely a stretch goal).

[motjuste]

sqa_tests should also produce a test_results.xml. In the near future, these results will then show up individually in Test Observer, SQA's dashboard. More info available in spec SQ088.