WIP Lightning Indexer + DSA/HCA API

[Micky774]

Description

This PR contains:

1. Lightning indexer fwd/bwd hybrid implementations, using partial fused Triton kernels
2. Fused implementation of indexer+topk
3. API for DSA/HCA built on stubs for temporary staging and design (pending externally sourced kernels)
4. Benchmark scripts for the lightning indexer and indexer+topk
5. Rough integration of Triton kernels into JAX for ROCm

Note that in the PR that will eventually target/land on main, only the API changes and triton kernel integration will persist, with kernels being relocated elsewhere.

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

Changes

Please list the changes introduced in this PR:

• Change A
• Change B

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