Datamodules Refactor

[djdameln]

Changes to be made to the datamodules feature branch before merging into main.

• Create and implement new design for modules in anomalib/data.
• Add Data Module for Video dataset #646
• Add synthetic validation set functionality.
• Remove PreProcessor class and use raw transforms instead.
• Check if mask files exist when creating Folder dataset #680
• Use enum for task type
• Add support for Detection task type #732
• Allow custom val/test split ratio (see Changing ratio for create_validation_set #731)

[jpcbertoldo]

#634 one more down here, no?

[djdameln]

Yep, getting there. We're working on the last item, but we might decide to address it in a separate PR to main to speed up merging the feature branch.