[C/PyTorch] Userbuffers and comm+GEMM overlap algorithms refactored and moved to TE/common

[denera]

Description

This PR moves Userbuffers and comm+GEMM overlap algorithms from TE/PyTorch to TE/common with refactored interfaces to remove the PyTorch dependency.

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
• [x] Code refractor

Changes

• transformer_engine/pytorch/csrc/userbuffers moved to transformer_engine/common/comm_gemm_overlap/userbuffers.
• transformer_engine/pytorch/csrc/comm_gemm_overlap.h split into transformer_engine/common/include/transformer_engine/comm_gemm_overlap.h and transformer_engine/common/comm_gemm_overlap/comm_gemm_overlap.cpp and refactored to remove torch::Tensor dependency.
• Added new TE/PyTorch wrappers around the refactored comm+GEMM overlap algorithms.
• Expanded unit tests to cover all overlap algorithms including atomic GEMM overlaps (tested as AG+RS pairs).

Checklist:

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