dynamically test with all supported Python versions

[zacharyburnett]

uses fill: to fill in toxenvs py311, py312, py313 (reading requires-python: from pyproject.toml)

analogous to spacetelescope/jwst#10428

blocked by OpenAstronomy/github-actions-workflows#388 and release v2.6.3 of the OpenAstronomy workflows

this pr is on hold pending a better solution in the OpenAstronomy workflows

Tasks

• request a review from someone specific, to avoid making the maintainers review every PR
• add a build milestone, i.e. 24Q4_B15 (use the latest build if not sure)
• Does this PR change user-facing code / API? (if not, label with no-changelog-entry-needed)
  • write news fragment(s) in changes/: echo "changed something" > changes/<PR#>.<changetype>.rst (see changelog readme for instructions)
    • if your change breaks existing functionality, also add a changes/<PR#>.breaking.rst news fragment
  • update or add relevant tests
  • update relevant docstrings and / or docs/ page
  • start a regression test and include a link to the running job (click here for instructions)
    • Do truth files need to be updated ("okified")?
      • after the reviewer has approved these changes, run okify_regtests to update the truth files
• if a JIRA ticket exists, make sure it is resolved properly

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.00%. Comparing base (67d9afc) to head (c154650).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2256   +/-   ##
=======================================
  Coverage   81.00%   81.00%           
=======================================
  Files         159      159           
  Lines        9509     9509           
=======================================
  Hits         7703     7703           
  Misses       1806     1806           

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[zacharyburnett]

I've refactored this PR to do the following:

• make a dynamic list of Python versions that this package supports, that we can manually update at our own pace to increase the latest version (so that when Python 3.15 comes out the CI doesn't immediately fail)
• set static job names run tests (oldest supported Python, ubuntu-latest) and run tests with coverage (latest supported Python, ubuntu-latest), that we can then set as "required" in the branch protection rules but which will always align with our oldest and latest supported Python versions

[zacharyburnett]

(this PR basically copies the upcoming package template as closely as possible, so that rollout of that template will have minimal changes when it happens)

[zacharyburnett]

in the repository settings, before or after merging this PR we can change the current required checks:

check / check-dependencies
test / py311-oldestdeps-xdist-cov (ubuntu-latest)
test / py314-cov (ubuntu-latest)
test / py314-pyargs (macos-latest)

to

test / check-dependencies
test / run tests (oldest supported Python, ubuntu-latest)
test / run tests with coverage (latest supported Python, ubuntu-latest)

and remove the other version-specific ones