text: Title: [UX] `sky logs` should be able to tail the last lines of the logs instead of showing all logs
  Body: <!-- Describe the bug report / feature request here -->
  
  
  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.
  
  <!-- If relevant, fill in versioning info to help us troubleshoot -->
  _Version & Commit info:_
  * `sky -v`: PLEASE_FILL_IN
  * `sky -c`: PLEASE_FILL_IN
  