Remove support to `emptyDir` and add a validation for missing storage definition

[git-hyagi]

Is your feature request related to a problem? Please describe. Even though the emptyDir can be handy for the development/test of the operator, it brings confusion and unexpected behaviors on Pulp that, in the end, is more harmful than helpful.

Describe the solution you'd like We should remove the support for using emptyDir (not only to pulpcore pods, but maybe to postgres too) and add a validation if no storage (pvc/sc/objectstorage) is provided.