Note: this PR is on top of the changes from#4823 because the plotly.js version used in plotly.py is based on the jupyterlab extension code, and we needed a new place to store the plotly.js version. The widget seemed like a good place because all of the other javascript is removed in this PR.

Fixes#4779.

It appears that the entirepackages/javascript/jupyterlab_plotly directory contains code that is either used to support very old versions of jupyter lab/notebook/voila, or is not used at all. This PR removes the entire directory in favor of having a very smallpackages/python/plotly/js directory that contains only the widget code (see#4663 for adding the widget code into that directory).

The last time that the jupyter extension was significantly changed was 3 years ago in#3142.@fcollonval described the files in thepackages/javascript/jupyterlab_plotly directory inthis comment. He did add support for federated extensions (new jupyter lab/notebook build), but I wasn't able to find evidence that having an extension installed in jupyterlab >=3 or jupyter notebook >= 7 is even necessary for plotly.@fcollonval if you know of any reason that that isn't true, please let me know!

To test:

• Checkout branch
• Create a new python env (conda, mamba, pipenv, etc)
• git clean -f -x -d
• cd packages/python/plotly
• pip install -e .
• pip install jupyter
• Try it out in jupyter lab:jupyter lab
• Try it out in jupyter notebook:jupyter notebook