Refactor NVFP4 E5M3 quantization to use "nvfp4_v2" data type
- Updated references from "fp4_v2" to "nvfp4_v2" across multiple modules including model_free, nvfp, and export functionalities.
- Modified documentation to reflect the new data type and its properties.
- Adjusted unit tests to ensure compatibility with the new naming convention.
- Ensured backward compatibility by updating relevant configurations and checks.
Signed-off-by: Xin He <xin3.he@intel.com>
