[Managed Spot] Send the job status to S3 bucket

[Michaelvll]

Currently, we cache the spot job status locally whenever the user called sky spot status, which will return a bit confusing job table as some of the jobs may still be marked as RUNNING, while it may already be in terminal status as the controller is already autostop.

A better solution is that we upload the status to an object store periodically from the controller so that we can always get the up-to-date status.