See #11841

- Make Cloud instructions smoother by using ScopedBlocks (this
  component was not available during the first round of Cloud-specific
  edits).

- Add a Prerequisites section

- Use steps in H2 headers. The idea is that a user would follow
  each step to collect diagnostic information, then pose a question
  in the final "Ask for help" section.

- Add more detailed examples of debug logs and a goroutine dump, and
  explain a bit more how you would use this information.

- Remove the text about resetting teleport's state by deleting the
  data directory. This is a general-purpose guide to investigating
  issues,so it seemed more appropriate to reserve that kind of action
  for when a user determined what the issue was.

- Add instructions for getting your Teleport version in order to
  ask for help.

- Add a further reading section.