Offer migration of PVC contents

[ebaron]

#166 adds a configurable PVC spec. Once created, it's not possible to edit the PVC spec without deleting and recreating it. It would be useful to respond to an editted PVC spec in our CR by:

1. Creating a new PVC
2. Migrating the Flight Recordings and Templates from the old PVC to the new PVC
3. Deleting the old PVC

Perhaps there is an operator we could use to do this kind of thing.

[andrewazores]

Needs revisiting with 3.0's use of SeaweedFS for storage rather than direct PVC access. We would need to look at SeaweedFS migrations, or else it will become irrelevant if/when we open up the storage to allow users to drop in their own S3 provider.