Implement a classification pipeline

[AjeyPaiK]

Is your feature request related to a problem? Please describe.
Ahcore currently supports only segmentation tasks. It would be nice to have a classification pipeline along with some robust feature extractors.

Describe the solution you'd like

• Integrate a feature extractor from open source foundation models. (Eg: one avaliable from Owkin into the model zoo.) #67
• Implement a callback to store the feature vectors extracted by the foundation model. #66
• Implement a dataset that yields feature vectors reading H5 files. #63
• Implement classification models for downstream tasks that uses the extracted feature vectors. (Eg: DeepMIL) #64

Describe alternatives you've considered
N/A

Additional context
Might have to slightly change the behavior of H5TileFeatureWriter.