Fix ramp parsing and GENRAMP indexing in TCOPFLOW

[willagrace]

Merge request type

• New feature
• Resolves bug
• Documentation
• Other

Relates to

• OPFLOW
• SOPFLOW
• SCOPFLOW
• TCOPFLOW
• CMake build system
• Spack configuration
• Manual
• Web docs
• Other

This MR updates

• Header files
• Source code
• CMake build system
• Spack configuration
• Web docs
• Manual
• Other

Summary

This PR fixes two ramp related issues in TCOPFLOW.

Issue 1 (psreaddata.cpp):
Previously, generator ramp values were overwritten by fuel type defaults in TCOPFLOW. The updated logic only applies fuel-based default ramp rates when the corresponding MATPOWER ramp-rate value is unspecified.

Issue 2 (genramp.cpp):
Previously, some generators were not actually constrained by TCOPFLOW ramp-coupling constraints.
The previous implementation computed generator Pg locations by using PSBUSGetVariableLocation and adding 2 to the index to skip Va and Vm. This approach worked on the first generator, but failed otherwise. The fix uses each generator's stored active-power locations directly (startxpowloc and startxpowlocglob), so each active generator gets its own correct ramp constraint and Jacobian entries.

[pelesh]

Not scaling ramp rates by the generator MVA base may be a bug.

The code needs to be documented better. Please insert comments describing what the code does (or what is the intention behind the code).