Flaky kernel startups

[DonJayamanne]

Over the past few days I've been seeing flaky CI with kernel startup issues. Basically the kernel doesn't start even after we've connected to it.

This is what jupyter does today

• send kernel info request
• wait for the response
• ensure we get messages on iopub

What can we do:

• send request for kernel info as soon as we establish connection
• don't wait for resonse for kernel info (we don't do this today)
  • Lets see from telemetry how bad things are rather than slowing the whole startup by waiting for response for kernel info
  • Add telemetry to see when we connect to kernels and its not ready (don't get response for kernel info)
• Probably send a second request for kernel info if we don't get the resopnse for first request in half of the timeout period
• Wait for shell & iopub ports to be used (i.e. kernel connects to these two ports)

[DonJayamanne]

Merged most of these fixes to main.

[DonJayamanne]

I think we've addressed the issues, closing this for now.