Packaging the tests

[jo-basevi]

Package up the tests so they can be installed via conda/pip and versioned.

It is possible to pass a package to pytest pytest --pyargs my-package which runs test code inside that package: https://docs.pytest.org/en/7.1.x/explanation/goodpractices.html#tests-as-part-of-application-code.
However, will need to test that custom command line args such as --control-path , --output-path etc still work (see https://stackoverflow.com/questions/41270604/using-command-line-parameters-with-pytest-pyargs). Otherwise will need to create wrapper commands that call pytest. (Will also need to restructure code into src and test, and add pyproject.toml etc.)

It will also need a think of how it is deployed in CI tests that is run on NCI. As the tests are currently run using the deployed payu module (https://github.com/ACCESS-NRI/payu-condaenv). This package can be added to this conda environment but then the version in the payu conda environment is fixed - which could be fine when the package is in a stable state or the environment can be redeployed with an updated version.

[jo-basevi]

Versioning tests were discussed in this issue #12, so older configurations can run earlier versions of test code.

[jo-basevi]

Also add CI to test packaging, and also CI to run any local tests

[jo-basevi]

Could use pip install PACKAGE_NAME as part of CI tests in access-om2-configs and reproducibility. A potential issue is in repro tests run on NCI, if there were two concurrent repro tests which were installing different versions