fix(controller): Determine registry address during start

Before this change re-deploying apps failed when the registry was re-scheduled to a different instance in the cluster.

Fixes #1128

- [x] Store just the image name and tag in the build model
- [x] Prefix the image reference before fleet pulls the image
- [x] Prefix the image reference before controller pushes config changes to the registry
- [x] Allow to migrate from existing releases
- [x] Don't block #1412
why do we need to add this field in? is it really necessary?