bump: testing with latest `torch` 2.6 (#20509)

* bump: testing with future torch 2.6
* bump `typing-extensions`
* TORCHINDUCTOR_CACHE_DIR
* bitsandbytes
* Apply suggestions from code review
* _TORCH_LESS_EQUAL_2_6

---------

Co-authored-by: Luca Antiga <luca.antiga@gmail.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Luca Antiga <luca@lightning.ai>