VS Code: Extensions and settings are not persisted

[vexingly]

The current implementation in the JupyterLab/RStudio/SAS images is broken and does not properly persist user settings or downloaded extensions in the built in VS Code server.

The remote desktop image has been updated and doesn't have the same configuration as these images anymore. Recommend that all images use the same VS Code server configuration.

Recommend to review #1404 and consider switching the configuration back to keeping the settings and extensions in the users persisted (home) directory.

Default extensions and default settings could be copied to the users home directory on first startup of the notebook (but should not override their settings), this is critical for protected-b notebooks that need the default extensions.

[vexingly]

PR here: StatCan/aaw-kubeflow-containers#488
Also includes #1792
Additional fixes for performance and to resolve other testing issues
Having some problems with the current build... https://github.com/StatCan/aaw-kubeflow-containers/actions

[vexingly]

Ready for review StatCan/aaw-kubeflow-containers#517