⚡ Improve `Engine` Performance and Implementation

[shaneahmed]

• Improve Engines performance and implementation
• Redesigns PatchPredictor engine using the new EngineABC base class.
• The WSIs are now processed using the same code as for the processing the patches using WSI based dataloader.
• The intermediate output is saved as zarr for the WSIs to resolve memory issues.
• The output of model architectures should now be a dictionary.
• The output can be specified as AnnotationStore for visualisation using TIAViz.