[PyTorch Debug] NVFP4 debug stats support

[pggPL]

Description

This PR adds support for NVFP4 statistics: underflows and mse. I add them in seperate feature, because we may want to have a lot nvfp4-specific features added later.

Also, I renamed few variables from "fp8"-like to "quantization"-like. I cannot rename all of them - for example "is_fp8_gemm_enabled" which is an API call, so I left some of them.

Fixes # (issue)

Type of change

• Documentation change (change only to the documentation, either a fix or a new content)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Infra/Build change
• Code refactoring

Checklist:

• I have read and followed the contributing guidelines
• The functionality is complete
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[pggPL]

/te-ci pytorch

[timmoon10]

It may be worth raising a deprecation warning in the constructor or something. DisableFP8GEMM would also benefit from this.

[timmoon10]

With RHT, it's possible that the NVFP4 data has fewer zeros than the high-precision data, so this stat would be negative. It's not possible yet (we currently only apply RHT to the NVFP4 column-wise data) and it's probably beyond the scope of this PR, but it's something to consider if we ever generalize.