Update notebook execution timer

[msujew]

What it does

Does essentially as the title says. In vscode, the execution time display is updated every 100ms to show that the execution is still running. We just do the same.

How to test

1. Open a notebook and select a kernel
2. Start a long running execution, see:

import time
print('1')

time.sleep(2)

print('2')

time.sleep(2)

print('3')

3. The timer should behave as expected

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

[jonah-iden]

out of some reason its starting the counter at 2 seconds when executing a cell

theia_notebook-timer.mp4

so in this example the timer ends 2 seconds after the actual execution time

[jonah-iden]

The issue is probably that the clock on serverside has a bit of a differnent time than the one on the client machine.
Maybe when first starting the execution, one could calculate this difference and add that to the time when counting up. But i think this issue is negligible. So approved

[jonah-iden]

works like a charm now