WIP: Solution Pool

[whart222]

Fixes #3513 (partially) .

Summary/Motivation:

The alternative_solutions contrib package includes a rudimentary solution pool object. This PR includes a more comprehensive capability for defining and managing solution pools.

Changes proposed in this PR:

• PyomoPoolManager - Manages pools for Pyomo solutions
• SolutionPool* - Classes used to define various solution pools
• Functions in pyomo.contrib.alternative_solutions now use and return PyomoPoolManager instances.
• PyomoSolution - Function that returns a Solution object given Pyomo model data

NOTE: This is a WIP PR. I'm submitting this now to help define expectations for finalizing this new capability.

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.

[whart222]

Note that this PR now includes updates to the Bunch class defined in pyomo.common. I have been using the public Munch class, but these revisions align the Bunch API with Munch.

[codecov]

Codecov Report

Attention: Patch coverage is 90.61785% with 41 lines in your changes missing coverage. Please review.

Project coverage is 87.00%. Comparing base (10d6acc) to head (834cd95).

Files with missing lines	Patch %	Lines
pyomo/contrib/alternative_solutions/solnpool.py	88.54%	26 Missing ⚠️
pyomo/contrib/alternative_solutions/solution.py	90.09%	10 Missing ⚠️
pyomo/contrib/alternative_solutions/balas.py	81.81%	2 Missing ⚠️
...o/contrib/alternative_solutions/gurobi_solnpool.py	94.44%	2 Missing ⚠️
pyomo/contrib/alternative_solutions/aos_utils.py	92.30%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3657      +/-   ##
==========================================
- Coverage   89.05%   87.00%   -2.05%     
==========================================
  Files         890      820      -70     
  Lines      102617   101335    -1282     
==========================================
- Hits        91384    88167    -3217     
- Misses      11233    13168    +1935     

Flag	Coverage Δ
builders	?
linux	86.78% <90.61%> (-2.03%)	⬇️
linux_other	86.78% <90.61%> (+<0.01%)	⬆️
osx	83.11% <90.61%> (+0.01%)	⬆️
win	84.99% <90.61%> (+0.01%)	⬆️
win_other	84.99% <90.61%> (+0.01%)	⬆️

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