Improve latency metrics
Right now all we display is upload latency. We could display additional latency metrics from GraceDB to get a fuller look at the downstream alert infrastructure latency:
- latency of PASTRO_READY label
- latency of SKYMAP_READY label
- latency of PE reports, DQ reports, etc.
Everything uploaded to GraceDB should be timestamped so in principle we could collect these metrics for any metadata applied.