Add pytest to daqpytools

[emmuhamm]

Description

Fix #39

Add tests.

NGL pretty much all of this is copilot generated. However I did ask it to make most of the relevant ones and I did go through it to see if it makes sense. I've checked it and to my knowledge its doing what it needs to do.

Type of change

• New feature or enhancement (non-breaking change which adds functionality)

Testing checklist

Run pytest and see if it works

• Unit tests pass (e.g. dbt-build --unittest)
• Minimal system quicktest passes (pytest -s minimal_system_quick_test.py)
• Full set of integration tests pass (daqsystemtest_integtest_bundle.sh)
• Python tests pass if applicable (e.g. python -m pytest)
• Pre-commit hooks run successfully if applicable (e.g. pre-commit run --all-files)

Further checks

• Code is commented where needed, particularly in hard-to-understand areas
• Code style is correct (dbt-build --lint, and/or see https://dune-daq-sw.readthedocs.io/en/latest/packages/styleguide/)
• If applicable, new tests have been added or an issue has been opened to tackle that in the future.
  (Indicate issue here: # (issue))