MPC Load Data Ignore Expressions

[eslickj]

Fixes None

Summary/Motivation:

When loading MPC data into a model, if a data key is an Expression, the model will get messed up because the expression will be replaced. This PR makes loading MPC data into a model ignore expressions.

Changes proposed in this PR:

• Ignore expressions when loading MPC data into a model
• When interpolating MPC data if a data point is None make the interpolated value None

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.

[codecov]

Codecov Report

❌ Patch coverage is 90.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 89.60%. Comparing base (7ad143c) to head (b0eddf5).

Files with missing lines	Patch %	Lines
pyomo/contrib/mpc/interfaces/load_data.py	85.71%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3868      +/-   ##
==========================================
- Coverage   89.67%   89.60%   -0.08%     
==========================================
  Files         908      908              
  Lines      106735   106744       +9     
==========================================
- Hits        95717    95643      -74     
- Misses      11018    11101      +83     

Flag	Coverage Δ
builders	29.08% <10.00%> (-0.01%)	⬇️
default	85.96% <90.00%> (?)
expensive	35.51% <10.00%> (?)
linux	86.71% <90.00%> (-2.46%)	⬇️
linux_other	86.71% <90.00%> (-0.43%)	⬇️
oldsolvers	28.00% <10.00%> (+<0.01%)	⬆️
osx	82.04% <90.00%> (+<0.01%)	⬆️
win	85.13% <90.00%> (-0.43%)	⬇️
win_other	85.13% <90.00%> (-0.43%)	⬇️

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

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.