Fix for compatibility with pandas 1.5.x

[ghackebeil]

Addresses #36

• relaxes version constraint for pandas to include 1.5.x
  • avoid using groupby(...).apply(..., include_groups=False)
• extend tests to cover get_region_dispatch_summary
  • this was mainly to check that some other groupby statements weren't producing the pandas DeprecationWarning related to this include_groups keyword added in pandas 2.x
• fix 2 exception messages that weren't passing enough arguments to str.format

Test workflow changes:

• Update test matrix to include testing with pandas 1.x + numpy 1.x
• Adding setup-python action to fix issue in macos-latest builds where uv would always use python3.13 (no matter what python-version was enabled)
• Dropping python 3.8 testing since it is past EOL
• Adding python 3.13 testing (with a few excludes to avoid unrelated build failures)

[ghackebeil]

If it's okay with you, I'll also add another build parameter to test the project on both pandas 1.x and 2.x. I'll wait until I see "workflow approval" on this PR to modify the cicd.yml file and push those changes as well.

[ghackebeil]

@nick-gorman: Any chance you have a moment to approve this PR for test workflow?

[ghackebeil]

Figured out how to run the action workflows on my fork. Updated description with test workflow changes.

[nick-gorman]

@ghackebeil Can you push an empty/trivial commit so we can see if that triggers the testing workflow?

[ghackebeil]

Sure! Will push something shortly.

[ghackebeil]

I need to fix the author on my last commit, sorry. Going to do a force push again to my fork in a moment.

[ghackebeil]

Good to go now. Here's a link to where the tests are running on my fork, if that helps (in case they don't run here):
https://github.com/ghackebeil/nempy/actions/runs/18577563489

[ghackebeil]

I'll try to figure out what is with the build errors. Things were passing before now.

[ghackebeil]

Latest build looks good, @nick-gorman.
https://github.com/ghackebeil/nempy/actions/runs/18582977311