[JS] [Docs] improve googleCloud IAM role documentation and logging

[MichaelDoyle]

1. Documentation for google-cloud does not mention the required IAM roles for telemetry.
   1. Cloud Trace Agent (Tracing/Spans)
   2. Logs Writer (Logs)
   3. Monitoring Metrics Writer (Metrics)
2. Error messages do not provide helpful information on what IAM roles are missing or how to add them.

Particularly, for Firebase App Hosting, logging can be a bit misleading, because Cloud Run will also write some server logs, and those will be visible.