Slow execution of all cells in Notebooks when working on large notebooks with image outputs

[DonJayamanne]

Does this issue occur when all extensions are disabled?: Yes/No

• VS Code Version: N/A
• OS Version: N/A

Steps to Reproduce:

1. Create a Jupyter notebook
2. Add a code cell with the following code

from IPython import display
display.Image("<valid path>/output.png")

3. Run the above cell
4. Now copy and paste this cell a few 100 times, at least 200-300 times
5. Save the notebook
6. Run one cell verify the cell runs
7. Open Jupyter extension logs (output panel) and clear it
8. Hit run all button
9. Problem 1: Notice that Jupyter extension logs do not get updated with anything and execution does not start for a few seconds.
   Depending on the machine this can take a few seconds, event 40s.
   After 40s, Jupyter extension finally gets the message from VS Code renderer process to run the cells
   Now cells run to completion in 3-5s.
10. Problem 2: Now run a single cell, and we can still see the same delays.

Summary

• Perception is execution takes a few minutes
• In reality Jupyter extension runs in a few seconds (<5s)
• VS Code renderer process is busy doing something when we hit run all

[DonJayamanne]

Closing as fixed

[DonJayamanne]

Addressed as part of #209787