GitLab Sourcegraph.com production readiness

Created by: keegancsmith

This issue is to track the work we will do in the 3.11 release milestone to ensure Sourcegraph.com is production ready for GitLab.com using Sourcegraph.com as an opt-in code intelligence provider. An RFC still needs to be fleshed out, but the high level themes will be operational:

• Load shedding / rate limiting - If something goes wrong, can we isolate the effects.
• Observability (likely in a good place after distribution's work on this)
  • Dashboards on general health.
  • Dashboards on code intelligence health.
• Pre-emptive load test

This is all work we have done before, so hopefully we will just be reviving it.