feat: RandomLigandTransform to perform system level ligand transformation (to be used in training)

[akdel]

• Removes keyword argument structure_transforms in PinderDataset and PinderLoader and replaces with structure_transforms_target and structure_transforms_feature
  • The behavior is largely the same, but this change allows application of different transforms to the "feature" complex vs. the ground-truth complex
  • An example transform is added which operates on the ligand chain to introduce random rotations (this is an example of a transform that would be applied to the feature complex and not the ground-truth target complex

[codecov]

Codecov Report

Attention: Patch coverage is 92.00000% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/pinder-core/pinder/core/loader/loader.py	50.00%	0 Missing and 2 partials ⚠️

Flag	Coverage Δ
	79.93% <92.00%> (+0.09%)	⬆️

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Files with missing lines	Coverage Δ
src/pinder-core/pinder/core/loader/transforms.py	87.50% <100.00%> (+6.10%)	⬆️
src/pinder-core/pinder/core/loader/loader.py	76.73% <50.00%> (-0.27%)	⬇️

... and 5 files with indirect coverage changes