codeintel: Update metrics

Created by: efritz

Update the frontend and precise-code-intel-worker dashboards to have the following data:

• processor error rates
• queue size + growth rate
• latencies and error rates for
  • gitserver calls
  • dbstore calls (postgres)
  • lsifstore calls (codeintel-db)
  • uploadstore calls (minio, gcs, s3)

Added monitoring spans by hand after removing the observability layers in https://github.com/sourcegraph/sourcegraph/pull/15534.