Add ParameterizedQuadraticRepn and corresponding expression walker

[shermanjasonaf]

Summary/Motivation:

With upcoming changes to the preprocessing subroutine of the contributed PyROS solver, and, in particular, the preprocessor's coefficient matching step, which requires analyzing expression trees in terms of selected variables only, this PR adds a ParameterizedQuadraticRepn object that has the same structure as the existing QuadraticRepn (of #2823), and an accompanying expression walker that extends the behavior of the QuadraticRepnVisitor and ParameterizedLinearRepnVisitor (of #3268) to allow for collection of quadratic/bilinear terms with potentially variable coefficient expressions. As with the ParameterizedLinearRepnVisitor, variables to be treated as data are specified through the wrt argument to the ParameterizedQuadraticRepnVisitor constructor.

Changes proposed in this PR:

• Add ParameterizedQuadraticRepn class that inherits from QuadraticRepn but re-implements all methods/attributes that assume that constants and coefficients are numbers rather than expressions.
• Add ParameterizedQuadraticRepnVisitor that inherits from ParameterizedLinearRepnVisitor and features:
  • redefined exitNode handlers for products of linear expressions and products of quadratic/nonlinear expressions
  • a redefined finalizeResult method
  • expansion of nonlinear products by default

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.55%. Comparing base (b480497) to head (7ab6270).
Report is 30 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3324      +/-   ##
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+ Coverage   88.52%   88.55%   +0.03%     
==========================================
  Files         868      869       +1     
  Lines       98436    98687     +251     
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+ Hits        87144    87396     +252     
+ Misses      11292    11291       -1     

Flag	Coverage Δ
linux	86.08% <100.00%> (+0.04%)	⬆️
osx	75.73% <100.00%> (+0.06%)	⬆️
other	86.58% <100.00%> (+0.03%)	⬆️
win	83.89% <100.00%> (+0.04%)	⬆️

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[jsiirola]

This has a huge amount of repeated code (from a mix of parameterized_linear and quadratic. In the future we should refactor the walkers so that we can make better use of mixins or more general methods to clean this up.