Add task related context keys

[msujew]

What it does

Addresses an issue found in #14725 (reply in thread).

Adds a few new task related context keys that are in use by the Python extension. See here.

How to test

1. Open a python file that simply contains a print("hello world") script.
2. Assert that the editor/title/run menu contains all expected entries:
   
3. Assert that these entries work as expected.

Review checklist

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

Reminder for reviewers

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