Per pipeline/task auto-pruning configurations

This is coming from SRVKP-1554,

Goal:

Allow customers to enable and configure an auto-prune function in the operator which would automatically run the pruning for pipelnerun and taskruns and clean up old objects and their related resources such as PVCs.

Currently, we the only granularity we provide to the pruner is at the namespace level, but nothing at the pipeline/task level

Acceptance Criteria

• Admin can configure the operator to automatically prune the pipelinerun with the following configurations
  • Keep last N pipelineruns for each pipeline
  • Keep pipelineruns younger than D days for each pipeline