[KNITRO] Add objective bound retrieval for MIP

[eminyouskn]

Fixes # .

Summary/Motivation:

This PR add the objective bound retreival for MIP when KNITRO is used as solver.

Changes proposed in this PR:

Legal Acknowledgement

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

@mrmundt Sorry for adding another PR.

[mrmundt]

@mrmundt Sorry for adding another PR.

RUDE. (Kidding, thanks for doing this 😄 )

[codecov]

Codecov Report

❌ Patch coverage is 83.33333% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 89.40%. Comparing base (bb1203d) to head (285866c).
⚠️ Report is 8 commits behind head on main.

Files with missing lines	Patch %	Lines
pyomo/contrib/solver/solvers/knitro/engine.py	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3826      +/-   ##
==========================================
- Coverage   89.40%   89.40%   -0.01%     
==========================================
  Files         903      903              
  Lines      105380   105386       +6     
==========================================
+ Hits        94214    94218       +4     
- Misses      11166    11168       +2     

Flag	Coverage Δ
builders	29.14% <16.66%> (-0.01%)	⬇️
default	86.02% <83.33%> (?)
expensive	34.84% <16.66%> (?)
linux	86.75% <16.66%> (-2.42%)	⬇️
linux_other	86.75% <16.66%> (-0.01%)	⬇️
osx	82.91% <16.66%> (-0.01%)	⬇️
win	84.98% <16.66%> (-0.01%)	⬇️
win_other	84.98% <16.66%> (-0.01%)	⬇️

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