[UX] sky logs should be able to tail the last lines of the logs instead of showing all logs

[Michaelvll]

We should have a way to only tail the logs for the last few lines and follow the outputs with sky logs. Otherwise, if a user have a long log file for a job, it will print a lot of messages on the screen when they run sky logs after a while.

Version & Commit info:

• sky -v: PLEASE_FILL_IN
• sky -c: PLEASE_FILL_IN

[Michaelvll]

Fixed by #4241. Closing.