[Feature]: Naming conventions for output files

[JesseJenkins]

Feature description

The output file naming conventions are a bit inconsistent/unclear currently. Examples:

• ReserveMargin.csv is actually the shadow prices of the capacity reserve margin constraints. It should probably be called ReserveMarginPrices.csv
• Some names are UpperCaseName while others are Snake_Case and still others are Snake_case or Uppercase.
• It looks like the required output files are all lowercase names, while the settings-specific outputs are some version of the above formats. I guess that is fine. But we should be consistent in the naming of the settings-specific outs.

Motivation

This just cleans up naming conventions and clarifies (for some) what the content is.

Implementation strategy

Choose a unified naming convention. Revise ReserveMargin.csv -> ReserveMarginPrices.csv for clarity.

This will be a breaking change so wait to push to Main until a version update. Add to Develop when complete.

Additional context

No response