Fixed context keys for notebook editor context

[jonah-iden]

What it does

This fixes the setting of context keys for editor level context keys. Only implements some of the keys currently (see notebook-context-manager.ts).
This makes jupyter commands like Export As or Restart Kernel available in the notebook editor toolbar

How to test

1. Have the python and jupyter extension installed.
2. After opening and clicking on a notebook the export command should pop up in the toolbar.
3. Then after selecting a kernel the restart kernel command should appear as well
4. both should be executable

Follow-ups

Implement the outline view for notebooks including the outline.focus command so that the Show Table of Contents command works as well

Review checklist

• As an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• As a reviewer, I agree to behave in accordance with the review guidelines

[msujew]

The behavior looks quite good. However, for some reason it breaks all code lenses (see failing tests). I can also reproduce this in the actual app:

[jonah-iden]

How did you reproduce it in the app?

[msujew]

@jonah-iden I enabled the TypeScript Reference Lens setting in the app and opened a .ts file. Clicking on the code lens yielded the error. I was also able to reproduce it by exporting a ipynb file to a .py file and using the Run Cell lens.

[jonah-iden]

should be fixed now

[jbicker]

LGTM