Add pytest matrix workflow

[jhkennedy]

This updates the pytest workflow to accept JSON input so that a matrix of python versions can be specified. Usage looks like:

  call-pytest-workflow:
    uses: ASFHyP3/actions/.github/workflows/reusable-pytest-matrix.yml@pytest-matrix
    with:
      local_package_name: hyp3_ci
      conda_env_name: hyp3-ci
      python_versions: >-
        ["3.8", "3.10"]

Notably, this chances the python version input from a string like "3.8" to a valid JSON list of strings and so is a breaking change.

This will require these PRs before we can release it as asf-tools, bullets, hyp3-autorift, and hyp3-gamma are all pointing at @main currently:

• Update GitHub Action workflows asf-tools#138
• Update actions bullets#18
• Enable dependabot for action version updates hyp3-autorift#163
• automate version updates for github actions hyp3-gamma#409

So I'm going to leave as draft for now until those are all done.

[jhkennedy]

Trufflehog can be ignored -- it's complaining about the removal of the git secrets config file and won't squawk anymore once we release.