Notebook unit testing

Notion task: https://www.notion.so/qim-dtu/Unit-test-for-notebooks-184bab83b2f980df8b99ebb8c4386c83

• Updated the notebooks to comply with the refactoring changes.
• Implemented unit tests for all notebooks (except annotation_tool.ipynb, segmentation_pipeline.ipynb, and Unet.ipynb). The unit tests are located in qim3d/tests/notebooks/test_notebooks.py.