Fix active notebook editor staying active as long as the editor is active

[jonah-iden]

What it does

This fixes the activeTextEditor should stay as the active cell as long as the associated notebook editor is also active.
This is important for extensions with a chat window that want to access the current selected code while the chat input is active

How to test

You can find a test extension including vsix here

You can use the Notebook-Test: get current selection to print out the current notebook selection or use the output channel to see the change events.

Even when for example selecting the workspace search or debug side panels, the selection inside the cell should still be available in the extension.

Follow-ups

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]

Good solution, thanks 👍