Address deprecations from persistence

[greg0ire]

A backwards-compatibility layer has been added to persistence to help consumers move to the new namespacing. It is based on class aliases, which means the type declaration changes should not be a BC-break: types are the same. See doctrine/persistence#71

This means:

• using the new namespaces
• adding autoload calls for new types to types that may be extended and use persistence types in type declarations of non-constructor methods, so that signature compatibility is recognized by old versions of php. More details on this at https://dev.to/greg0ire/how-to-deprecate-a-type-in-php-48cf

[greg0ire]

Seems like this has to do with https://github.com/doctrine/orm/pull/7079