Add Python 3.11 to CI

[WardBrian]

Submission Checklist

• Run unit tests
• Declare copyright holder and open-source license: see below

Summary

This adds the newly released Python 3.11 to the CI we run. Python 3.7 can be removed in 7 months (https://endoflife.date/python)

Copyright and Licensing

Please list the copyright holder for the work you are submitting (this will be you or your assignee, such as a university or company):

By submitting this pull request, the copyright holder is agreeing to license the submitted work under the following licenses:

• Code: BSD 3-clause (https://opensource.org/licenses/BSD-3-Clause)

[codecov-commenter]

Codecov Report

Merging #633 (7ad126c) into develop (b382cc3) will decrease coverage by 0.24%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop     #633      +/-   ##
===========================================
- Coverage    80.25%   80.01%   -0.25%     
===========================================
  Files           69       23      -46     
  Lines        10327     3442    -6885     
===========================================
- Hits          8288     2754    -5534     
+ Misses        2039      688    -1351     

Impacted Files	Coverage Δ
cmdstanpy/cmdstanpy/utils/command.py	77.08% <0.00%> (-8.34%)	⬇️
cmdstanpy/cmdstanpy/progress.py	76.19% <0.00%> (-1.09%)	⬇️
cmdstanpy/cmdstanpy/install_cmdstan.py	39.50% <0.00%> (-0.31%)	⬇️
a/cmdstanpy/cmdstanpy/cmdstanpy/compiler_opts.py
a/cmdstanpy/cmdstanpy/cmdstanpy/stanfit/runset.py
...tanpy/cmdstanpy/cmdstanpy/install_cxx_toolchain.py
.../cmdstanpy/cmdstanpy/cmdstanpy/stanfit/metadata.py
a/cmdstanpy/cmdstanpy/cmdstanpy/utils/__init__.py
.../cmdstanpy/cmdstanpy/cmdstanpy/stanfit/__init__.py
...ork/cmdstanpy/cmdstanpy/cmdstanpy/utils/stancsv.py
... and 39 more

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