Description of problem:

Default knative metrics are coming with kn_workqueue_depth and pruner expressions should be unified with tekton_pruner instead of tektoncd_pruner for all epressions

Prerequisites (if any, like setup, operators/versions):

Steps to Reproduce

1. Enable event based pruner and run few pipelines and let the pipelines be deleted or processed
2. Navigate to Observe > metrics and query with expression kn_workqueue_depth
   1. 
3. Also filter the pruner queries using sample expressions as below tektoncd_pruner_resources_deleted_total_total
   Expression name should start with tekton_pruner instead of tektoncd_pruner
   

Actual results:

Expected results:

Reproducibility (Always/Intermittent/Only Once):

Acceptance criteria: 

Definition of Done:

Build Details:

Additional info (Such as Logs, Screenshots, etc):

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