Make voila compatible with jupyterlab 4

[trungleduc]

Problem

Since JupyterLab 4.0 is just around the corner, I think for the next release (0.5.0), voila should be compatible with lab 4 and not lab 3.

Proposed Solution

• Update to jupyter-sever 2 (DRAFT: Server version 2.0 #1283)
• Update the jupyterlab frontend components to use the 4.0.0 series, it can fix some remaining issues of Switch to a lab-based app for the Voila frontend #846
• Use type when adding the preview to the main area. See Customize layout from settings jupyterlab/jupyterlab#11614 for more information

[jtpio]

Posting here one of the comments from #846 which could be addressed by updating to lab 4 packages:

We should now be able to update to the 4.0.0-alpha.x JupyterLab packages, which include the change from jupyterlab/jupyterlab#11537 to allow for mock services.

[jtpio]

FYI JupyterLab 4 final has been released: https://github.com/jupyterlab/jupyterlab/releases/tag/v4.0.0

[martinRenou]

We may be stuck waiting for ipywidgets to support lab 4 before being able to update Voila

[trungleduc]

for the ipywidgets PR, a simple version bump is enough?

[martinRenou]

Hopefully, some attempts have been made https://github.com/jupyter-widgets/ipywidgets/pull/3752/files

Galata needs to be updated there too

[jtpio]

As part of the update of the Voila Preview extension for JupyterLab, it would also be useful to use the type property when adding a preview to the main area. So end users could decide to open the preview in a different area if they would like to (via the settings).

This functionality was added to JupyterLab in jupyterlab/jupyterlab#11614.