Resolve incompatibilities between autosummary plugin and Sphinx 9.x

[jsiirola]

Fixes #N/A; Follow-on to #3815.

Summary/Motivation:

#3815 got the documentation builds running again, but the custom Sphinx extensions were not getting correctly activated / run. This PR is a follow-on that monkey-patches additional functions within Sphinx's autosummary extensions so that Pyomo's extensions will run correctly in Sphinx 9.x.

This PR also adds tests for verifying that Sphinx is generating correct html:

• verify that our Sphinx extension is actually runing and generating the correct outpput
• verify that the bug (Type annotations appearing as invalid cross-reference sphinx-doc/sphinx#14223) is not manifesting in the rendered HTML

(Note that this PR will initially fail tests -- I am checking that the new unit tests pick up the sphinx-doc/sphinx#14223 error)

This PR will also disallow 9.0.x and 9.1 because of the reference bug.

Changes proposed in this PR:

• clean up / document the Sphinx extension
• Add additional monkeypatches to work around ausosummary not honoring autodoc_use_legacy_class_based
• Add tests to catch the recent doc build errors
• Disallow recent (9.x) Sphinx releases

Legal Acknowledgement

By contributing to this software project, I have read the contribution guide and agree to the following terms and conditions for my contribution:

1. I agree my contributions are submitted under the BSD license.
2. I represent I am authorized to make the contributions and grant the license. If my employer has rights to intellectual property that includes these contributions, I represent that I have received permission to make contributions and grant the required license on behalf of that employer.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.43%. Comparing base (c9ebf1a) to head (45f612d).
⚠️ Report is 24 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3818      +/-   ##
==========================================
- Coverage   89.43%   89.43%   -0.01%     
==========================================
  Files         906      905       -1     
  Lines      105445   105422      -23     
==========================================
- Hits        94307    94286      -21     
+ Misses      11138    11136       -2     

Flag	Coverage Δ
builders	29.12% <ø> (-0.03%)	⬇️
default	86.05% <ø> (?)
expensive	35.75% <ø> (?)
linux	86.74% <ø> (-2.46%)	⬇️
linux_other	86.74% <ø> (-0.01%)	⬇️
osx	82.92% <ø> (ø)
win	85.00% <ø> (ø)
win_other	85.00% <ø> (ø)

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[mrmundt]

I am fine with this as-is but have one silly nitpick.