Add support for sample_stats group in pymc.testing.mock_sample

[williambdean]

Description

This allows users to create sample_stats group in the mock sample helper

TODO:

• Way to specify these in the setup and teardown helper

However, I might wait on this item... Any thoughts if that is needed to get this through?

Related Issue

• Closes #
• Related to #

Checklist

• Checked that the pre-commit linting/style checks pass
• Included tests that prove the fix is effective or that the new feature works
• Added necessary documentation (docstrings and/or example notebooks)
• If you are a pro: each commit corresponds to a relevant logical change

Type of change

• New feature / enhancement
• Bug fix
• Documentation
• Maintenance
• Other (please specify):

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📚 Documentation preview 📚: https://pymc--7887.org.readthedocs.build/en/7887/

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.95%. Comparing base (0960323) to head (1c19384).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7887   +/-   ##
=======================================
  Coverage   92.94%   92.95%           
=======================================
  Files         116      116           
  Lines       18851    18859    +8     
=======================================
+ Hits        17521    17530    +9     
+ Misses       1330     1329    -1     

Files with missing lines	Coverage Δ
pymc/testing.py	90.14% <100.00%> (+0.16%)	⬆️

... and 1 file with indirect coverage changes

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