Integrate Script Editor with JupyterLab debugger

[karlaspuldaro]

The debugger extension will be part of lab core on its 3.0 release.
In lab 2.x, installing the debugger extension package separately didn't work on python editor.
In lab 3.0 it is now possible to use the debugger tool the same way as with regular file editor, by opening a python console for it and running the code there.

We want to be able to fully integrate the debugger with script editor (ie. without creating a console for it).

User Experience

• User can add breakpoints to the editor as default
• New button on the toolbar: Run and Debug (creates a debugger session only when script is executed in debug mode)
  

Motivation

• Enhance the script editor programming experience (less steps to enable debugging features)
• Increase efficiency by adding resources at runtime

High level planning

• how to enable the debugger
  • toggle vs run + run and debug (start debug session)
• how to define breakpoints
• how to show debugger UI while running