Edit the Database Access GUI guide for Cloud users (#11801)
Edit the Database Access GUI guide for Cloud users (#11801)

* Edit the Database Access GUI guide for Cloud users

See #10637

- Add a Prerequisites section with tabs for different scopes
- Use a ScopedBlock so the "Get connection information" section only
  shows connection options that are relevant to a particular scope.
- Where the guide refers to a particular "tsh" command that doesn't
  apply to all scopes, refer to the "Get connection information"
  section instead.
- Light copy-edits for style, clarity, and grammar

* Respond to PR feedback
gravitational/teleport,gravitational/teleport,gravitational/teleport,gravitational/teleport,gravitational/teleport,gravitational/teleport