Add more Verify / CI metrics to the stage dashboard

Description

Temporary dashboard: https://dashboards.gitlab.net/dashboard/snapshot/GgJ2C7ZxWlAWe72MeV9hYSGTWtiOOc6W

New metrics in Verify / CI stage dashboard:

Builds queuing metrics

• Rate of builds queuing operations
• Rate of builds queuing results
• Duration of the big query used to retrieve the queue histogram
• Queue size per runner type histogram
• Queue depth per result histogram

Pipeline creation metrics

• Pipelines created aggregated rate
• Pipelines created by pipeline source rate
• Pipeline creation duration histogram
• Pipeline size histogram

Pipeline processing

• Pipeline processing events rate

Future work

• Collapse everything by default ➡ gitlab-com/gl-infra/scalability#994