Remove from_data conversions in backends

[laggui]

Checklist

• Confirmed that run-checks all script has been executed.

Related Issues/PRs

Follow-up to #2778

Changes

With the last PR, the data conversion happens at the tensor API level. Backends should not have behave differently to handle conversions themselves.

[codecov]

Codecov Report

Attention: Patch coverage is 94.44444% with 1 line in your changes missing coverage. Please review.

Project coverage is 83.67%. Comparing base (6015823) to head (3e0400e).

Files with missing lines	Patch %	Lines
crates/burn-ndarray/src/ops/int_tensor.rs	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2783      +/-   ##
==========================================
- Coverage   83.67%   83.67%   -0.01%     
==========================================
  Files         832      832              
  Lines      109524   109517       -7     
==========================================
- Hits        91643    91637       -6     
+ Misses      17881    17880       -1     

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