Pipeline log improvement

Created by: LinuxSuRen

What would you like to be added: There're a few things about the Pipeline log that we can improve:

• Select the stage and step which error happened
• User can see the whole log output instead of download it every time
  • User should be able to follow the log output. It'd be better to offer a switch button to do that
  • Be aware of the very big log data. In some cases, the log output might be huge. For example, the whole log output might be more than 1M. Don't let it consumes too much memory of the browser.
  • In some cases, the critical part of the log error output cannot be found from the steps log.
  • The log file download feature is useful only when you want to send it to someone instead of regular checking.

Why is this needed: The log output is the most important part when there're some errors happened. In my view, this is the reason why I think the priority of this improvement request is medium.

/area devops /priority medium