Add torchvision.transforms v1/v2 independent ToTensor() implementation

[liopeer]

Changes

• add ToTensor() transform that is independent of the imported torchvision.transforms version (v1 or v2)
• make it available for import from the lightly.transforms module
• add testing of output tensor:
  • correct dtype (from np.uint8 to torch.float32)
  • correct shape (from channel last to channel first)
  • value range: from [0, 255] to [0, 1]

[codecov]

Codecov Report

Attention: Patch coverage is 76.47059% with 4 lines in your changes missing coverage. Please review.

Project coverage is 84.88%. Comparing base (c22ee83) to head (d820430).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
lightly/transforms/torchvision_v2_compatibility.py	75.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1718      +/-   ##
==========================================
- Coverage   84.88%   84.88%   -0.01%     
==========================================
  Files         157      157              
  Lines        6537     6543       +6     
==========================================
+ Hits         5549     5554       +5     
- Misses        988      989       +1     

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[liopeer]

Additional Changes

• removed assertion statements & imported class directly as requested
• added missing docstring to the transform (tried to stay close to the docstrings of other transforms)
• renamed the module in which the transform resides to torchvision_v2compatibility to resolve name-space issues

[guarin]

LGTM! Feel free to resolve and merge my comment.