[Xpress] Remove deprecation warnings (#1)

[XPRSc4v4]

Hi!

Fixes

• Deprecated function names in Xpress 9.8+ (Python API v46)
• Removed enums in Xpress 9.8+
• Compatibility with both pre-9.8 and post-9.8 Xpress versions

Summary/Motivation:

Starting with Xpress 9.8 (Python API version 46), FICO deprecated lowercase function names in favor of camelCase (e.g., lpoptimize → lpOptimize) and removed several enum types. The old functions are still available but deprecated, and will be removed in future releases. This PR adds runtime version detection to dispatch to the correct functions and enums based on the installed Xpress version, eliminating deprecation warnings while maintaining backward compatibility.

Changes proposed in this PR:

• Extended version detection logic that checks Xpress Python API version at runtime
• Created compatibility wrappers that dispatch to correct function names (lowercase for v45-, camelCase for v46+)
• Updated enum handling to use new attribute access pattern for v46+ while maintaining old enum values for earlier versions
• Modified tests to use XpressDirect interface instead of calling Xpress Python APIs directly
• All changes maintain full backward compatibility with Xpress versions prior to 9.8

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 74.82014% with 35 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.40%. Comparing base (dcaba42) to head (13ee044).

Files with missing lines	Patch %	Lines
pyomo/solvers/plugins/solvers/xpress_direct.py	74.26%	35 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3794      +/-   ##
==========================================
- Coverage   89.42%   88.40%   -1.02%     
==========================================
  Files         909      909              
  Lines      105579   105675      +96     
==========================================
- Hits        94411    93419     -992     
- Misses      11168    12256    +1088     

Flag	Coverage Δ
builders	29.13% <28.77%> (+<0.01%)	⬆️
default	86.01% <58.99%> (?)
expensive	35.76% <28.77%> (?)
linux	85.68% <59.71%> (-3.51%)	⬇️
linux_other	85.68% <59.71%> (-1.05%)	⬇️
osx	?
win	84.96% <59.71%> (-0.04%)	⬇️
win_other	84.96% <59.71%> (-0.04%)	⬇️

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[blnicho]

This is changing the xpress version for every GHA job using conda to install Python packages which is not what I think you intended. During the dev call we talked about installing an older version of xpress on just one or two jobs to exercise the version-specific logic in the solver interface. I think you can do this by modifying the if-tree above that sets the XPRESS environment variable. There is already some special logic there for windows so maybe we use the linux conda job for this. I think you can just modify the else section on line 450 to something like:

if test "${{matrix.TARGET}}" == linux; then
    XPRESS='xpress<9.3'
else
    XPRESS='xpress'
fi

[XPRSc4v4]

Sorry, I should have asked for clarification during the call!
I've applied the changes, targeting Python 3.10 so the latest Xpress release is still tested in the other jobs. Let me know if there are any other issues.