Testing: add missing Ipopt guards (parmest); add GHA nosolvers test

[jsiirola]

Fixes # .

Summary/Motivation:

#3550 snuck in some tests that were improperly guarded for missing Ipopt solvers (this was caught by a Jenkins job that is not in the main PR workflow). This PR:

• adds the missing guards
• adds a linux/3.13/nosolvers GHA to catch this during the normal PR workflow.

Changes proposed in this PR:

• (see above)

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

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.10%. Comparing base (4a962b1) to head (a102e94).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3962      +/-   ##
==========================================
- Coverage   90.11%   90.10%   -0.01%     
==========================================
  Files         909      909              
  Lines      108551   108551              
==========================================
- Hits        97817    97814       -3     
- Misses      10734    10737       +3     

Flag	Coverage Δ
builders	29.09% <ø> (+<0.01%)	⬆️
default	86.10% <ø> (?)
expensive	35.12% <ø> (?)
linux	87.62% <ø> (-1.99%)	⬇️
linux_other	87.62% <ø> (ø)
oldsolvers	28.05% <ø> (+<0.01%)	⬆️
osx	83.07% <ø> (ø)
win	85.37% <ø> (-0.01%)	⬇️

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