Add metrics for Scheduled Pipeline Execution Policies

We currently have limited metrics for Scheduled Pipeline Execution Policies. We only track worker duration, which doesn't provide sufficient visibility into feature usage and impact on infrastructure.

We discussed this here

Proposal

Implement additional metrics to better understand the adoption and usage patterns of Scheduled Pipeline Execution Policies:

1. Unique namespaces with scheduled policies: Track the number of unique namespaces that have at least one scheduled pipeline execution policy configured.
2. Pipelines triggered by scheduled policies: Count how many pipelines are triggered specifically by scheduled pipeline execution policies.

Implementation Considerations

• For unique namespaces metric:
  • Similar to the existing metric for pipeline execution policies
  • Track at the namespace level to understand adoption across different organizations
• For triggered pipelines metric:
  • Implement within the pipeline creation process
  • Tag pipelines created via scheduled policies with appropriate metadata
  • Create counters to track these pipelines separately from other pipeline sources

Implementation plan: !189776 (merged)