Add a deployment-wide user secrets summary to the telemetry snapshot so
we can track adoption of user secrets
The summary reports:
- A breakdown of secrets by which injection fields are populated:
EnvNameOnly, FilePathOnly, Both, Neither
- The distribution of secrets per user (max, p25, p50, p75, p90)
All metrics are scoped to active non-system users. Soft-deleted users
are excluded. The percentile distribution is computed across the entire
active non-system user base, including users with zero secrets, so the
percentiles reflect deployment-wide adoption.
Assisted by Coder Agents.
Zach