Migrate OpenShift 4.20 release pipelines to use the common Konflux pipeline template from main branch, removing duplicate pipeline definitions and standardizing on shared configuration.

Why

The 4.18 pipelines are using older, duplicated pipeline definitions. Migrating to the common pipeline on main branch will:

• Reduce maintenance overhead (single pipeline to update)
• Ensure consistency across release branches
• Automatically inherit improvements made to the common pipeline

Acceptance Criteria

• .tekton/control-plane-operator-4-20-pull-request.yaml migrated to use common pipeline
• .tekton/control-plane-operator-4-20-push.yaml migrated to use common pipeline
• Both pipelines tested and passing
• Old pipeline definitions removed or deprecated

Technical Details

Here's the pipelineref to use:

  pipelineRef: 
    resolver: git
    params: 
      - name: url
        value: "https://github.com/openshift/hypershift.git"
      - name: revision
        value: main
      - name: pathInRepo
        value: .tekton/pipelines/common-operator-build.yaml

Since the pipeline is not in the same branch, it should not use the annotation that is used in the main branch pipelines that use the common pipeline

Files to Modify

• .tekton/control-plane-operator-4-20-pull-request.yaml
• .tekton/control-plane-operator-4-20-push.yaml

Migration Target

Common pipeline template on main branch