Migrate NR Authentication and JWT dashboards to Datadog

[robrap]

Note: It is unclear whether this will be owned by the Auth Squad or Arch-BOM, so this ticket is just collecting the appropriate information. These dashboards can be created when needed.

• Gist with Authentication and JWT Change Rollout - New Relic dashboard details

Authentication Dashboard screenshots:

JWT Change Rollout screenshots:

[dianakhuang]

We aren't sure whether or not we'll be doing the JWT work, so we're making it a P5 for now.

[robrap]

I'll note that Forgiving JWTs is so close to being complete, and it would be great if that were ticketed separately, and if we did the minimum dashboard work to land that work.