Add StatefulSet.Spec.PersistentVolumeClaimRetentionPolicy Override.

[MirahImage]

This closes #1231

Note to reviewers: remember to look at the commits in this PR and consider if they can be squashed

Summary Of Changes

Adds persistentVolumeClaimRetentionPolicy to the StatefulSet.Spec override.

[Dragane]

Thank you so much for working on this solution Mirah.

I would like to point out the bug (typo) in the CRDS file config/crd/bases/rabbitmq.com_rabbitmqclusters.yaml

There is a letter t missing:
persistenVolumeClaimRetentionPolicy instead of persistentVolumeClaimRetentionPolicy

[MirahImage]

Thanks for catching that!