Stream logs to files during VM provisioning and setup about skypilot

[franklsf95]

We should at least stream the logs to files and tell user to tail -F path/to/logfile if they're curious about progress. When I try it now I have to stare at a blank screen for 10 minutes with no progress:

I 11-16 19:37:15 cloud_vm_ray_backend.py:210] Launching on AWS us-west-2 (us-west-2a,us-west-2b,us-west-2c,us-west-2d).
I 11-16 19:37:15 cloud_vm_ray_backend.py:213] If this takes longer than ~30 seconds, provisioning is likely successful. Setting up may take a few minutes.
I 11-16 19:37:15 backend_utils.py:38] Created or updated file config/aws-ray.yml

[concretevitamin]

Yes, expected to not show, although we can change. The rationale is if you print ray up's stdout/stderr, and if you have retries, that will be very crowded. Give it a try by setting a p3.16x requirement.

We could try to write the stdout/stderr (captured in variables) to files. This is similar to V1's logging.

[concretevitamin]

+1 to stream to a file and hint on tail -f.