Support private container registry for Tekton Pruner

[jb-2020]

Feature request

Currently, we can set IMAGE_JOB_PRUNER_TKN - which we add to the operator’s deployment environment variables. This will override the image used by the operator for configuring the pruner's Job.

However, there does not seem to be any flag to specify imagePullSecrets for this Job.

Use case

Use a private container repository for the various images installed by the operator.

Note: Tekton Pruner is one example, need to ensure any K8s objects created by the operator support private container registries if applicable.