Fix extra comma in cnetstats output

[tgiroux]

Description

There were a few places in ControlNetFilter and ControlNetStatistics responsible for an extra comma being produced in the flat file output. Most changes are straightforward.
Removing the comma in ControlNetFilter::CubeStatsHeader required that I prepend a comma to a few strings in places where CubeStatsHeader is called.
I also updated the tests so everything should be passing.

Related Issue

#3700

Motivation and Context

How Has This Been Tested?

Ran cnetstats on some test input before and after my changes to validate that the extra comma is no longer produced.
All cnetstats gtests passed on linux.

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Documentation change (update to the documentation; no code change)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have read and agree to abide by the Code of Conduct
• I have read the CONTRIBUTING document.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.
• I have added myself to the .zenodo.json document.
• I have added any user impacting changes to the CHANGELOG.md document.

Licensing

This project is mostly composed of free and unencumbered software released into the public domain, and we are unlikely to accept contributions that are not also released into the public domain. Somewhere near the top of each file should have these words:

This work is free and unencumbered software released into the public domain. In jurisdictions that recognize copyright laws, the author or authors of this software dedicate any and all copyright interest in the software to the public domain.

• I dedicate any and all copyright interest in this software to the public domain. I make this dedication for the benefit of the public at large and to the detriment of my heirs and successors. I intend this dedication to be an overt act of relinquishment in perpetuity of all present and future rights to this software under copyright law.

[acpaquette]

Looks good!

[acpaquette]

XD