Instrument search apiserver metrics + tracing

[scotwells]

Summary

Think through and implement what metrics we should capture from the apsierver as its processing requests. These would be custom metrics that aren't already represented in the base apiserver metrics (e.g. requests sent to Meilisearch, etc).

Also confirm request tracing works as expected. Add trace spans for critical behavior we should have visibility on in traces.

Acceptance Criteria

• Document the metrics are exposed from the apiserver
• Implement metrics and tracing in apiserver
• Confirm metrics and traces are captured in test environment