reorganize tests, make devdeps testing optional, and unpin latest Python testing

[zacharyburnett]

Resolves SCSB-79

This PR reorganizes CI tests and moves devdeps tests to a new optional workflow that can be started with the label run devdeps tests

Checklist

• [x] ~added entry in CHANGES.rst (either in Bug Fixes or Changes to API)~
• [x] updated relevant tests
• [x] ~updated relevant documentation~
• [ ] updated relevant milestone(s)
• [x] added relevant label(s)

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (5756fda) 84.31% compared to head (08d6710) 84.31%. Report is 1 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #213 +/- ## ======================================= Coverage 84.31% 84.31% ======================================= Files 35 35 Lines 6452 6452 ======================================= Hits 5440 5440 Misses 1012 1012 ```

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[hbushouse]

github doesn't want to let me create a review, despite the fact that I've been tagged as a reviewer.

[hbushouse]

github doesn't want to let me create a review, despite the fact that I've been tagged as a reviewer.

Nevermind, it suddenly decided to let me review again.