A few more GDP examples

[sadavis1]

Fixes # .

Summary/Motivation:

Early in the summer, I worked on a few GDP example problems, the first of which was merged in #2838 . This PR contains the other two GDP example problems from Sawaya (2006) that I implemented. The code solves simple geometric problems and draws pretty pictures.

Changes proposed in this PR:

• Add "Circles" and "Farm Layout" example code and instance data
• Add matplotlib drawing code for each

Legal Acknowledgement

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1. I agree my contributions are submitted under the BSD license.
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[codecov]

Codecov Report

Patch coverage has no change and project coverage change: -0.01% ⚠️

Comparison is base (0e0f0cd) 88.09% compared to head (448b14a) 88.08%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2932      +/-   ##
==========================================
- Coverage   88.09%   88.08%   -0.01%     
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  Files         769      769              
  Lines       89493    89493              
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- Hits        78836    78832       -4     
- Misses      10657    10661       +4     

Flag	Coverage Δ
linux	85.18% <ø> (-0.01%)	⬇️
osx	74.99% <ø> (ø)
other	85.36% <ø> (ø)
win	82.43% <ø> (ø)

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see 1 file with indirect coverage changes

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[emma58]

This looks good! Just a few nits.

[bernalde]

This might be a more involved discussion than this PR, but where should we draw the line between a set of examples, tests, and supported models? In particular, for GDP, we have GDPLib https://github.com/SECQUOIA/gdplib, which could host these two examples. What's the motivation for adding them to the main Pyomo repository?

[blnicho]

@bernalde I think this is a great discussion to have outside of this PR. We are inconsistent with how examples are written and tested and also with where they live (both within and outside of the Pyomo repo). I'll open a PEP to start a more comprehensive discussion on this but I don't think this PR needs to wait for it to be resolved.

[sadavis1]

I've made the fixes requested, but I can't answer the broader question about where examples should live and how or if they should be tested. These aren't tested for now, since none of their neighbors were.

[blnicho]

@sadavis1 I cancelled the tests to free up GHA resources while we're finalizing things for the release. I'll relaunch them when we're done.