Change the current single form-based tool nnUNet GUI structure to multi-tabs style.

The tool GUI can have 2 tabs:

1. "Model Management" tab containing options to select python path, choose the results folder and download pre-trained models.
2. "Application" or "Inference" tab containing other dropdowns & buttons to select appropriate options specific to the inferencing process.,

Furthermore, dynamic features such as:
Tab 2 activated only when Tab 1's options such as the python path are aptly selected;
can be implemented.