Refactor CubeCL slices

[nathanielsimard]

Update rev from cubecl: tracel-ai/cubecl#644

[codecov]

Codecov Report

Attention: Patch coverage is 61.53846% with 10 lines in your changes missing coverage. Please review.

Project coverage is 81.10%. Comparing base (009ad59) to head (bba776f).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/burn-cubecl-fusion/src/shared/io.rs	70.58%	5 Missing ⚠️
crates/burn-cubecl-fusion/src/shared/kernel.rs	37.50%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3104      +/-   ##
==========================================
- Coverage   81.13%   81.10%   -0.03%     
==========================================
  Files         816      816              
  Lines      117417   117376      -41     
==========================================
- Hits        95263    95196      -67     
- Misses      22154    22180      +26     

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