Capture HiGHS output when initializing model

[jsiirola]

Fixes #3003

Summary/Motivation:

#3003 pointed out that the APPSI HiGHS interface does not capture output that HiGHS emits when initializing the first model. This PR adds additional output capturing within set_instance(), as well as a test to verify that the output is correctly being captured.

Changes proposed in this PR:

• Capture output emitted by HiGHS during set_instance()
• Test this behavior (relying on subprocess to capture initial output from HiGHS)

Legal Acknowledgement

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

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (bdbcb31) 88.10% compared to head (97d7509) 88.08%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3005      +/-   ##
==========================================
- Coverage   88.10%   88.08%   -0.02%     
==========================================
  Files         769      769              
  Lines       89520    89525       +5     
==========================================
- Hits        78869    78862       -7     
- Misses      10651    10663      +12     

Flag	Coverage Δ
linux	85.19% <92.30%> (+<0.01%)	⬆️
osx	74.99% <0.00%> (-0.01%)	⬇️
other	85.36% <92.30%> (+<0.01%)	⬆️
win	82.43% <92.30%> (-0.02%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
pyomo/contrib/appsi/solvers/highs.py	92.35% <92.30%> (+0.07%)	⬆️

... and 2 files with indirect coverage changes

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