[Kernels] Refactor function handling

[vasqu]

This will depend on a new kernels version, see huggingface/kernels#622

Updates to always use layer repos instead of function repos which also depends on kernels community PRs

1. rotary: Refactor split into separate files + warning in readme kernels-community#949
2. liger-kernels: Add layer repos for remaining functions kernels-community#995
3. aiter-rope: Add layer repo for apply_rotary_transformers kernels-community#996 cc @Abdennacer-Badaoui

TODOs

• bump respective kernels version (docs fail because kernels is installed?)

[github-actions]

[For maintainers] Suggested jobs to run (before merge)

run-slow: afmoe, apertus, arcee, aria, bitnet, csm, cwm, dbrx, deepseek_ocr2, deepseek_v3, deepseek_v32, dia, diffllama, doge, dots1, emu3

[github-actions]

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