Deprecate before dropping CDI.setCDIProvider

CDI.setCDIProvider allows to switch the cdi provider at any time by anyone. This lead to issues integrating multiple libraries doing it + is not a real user facing API, it is actually a server internal.

Proposal is to deprecate the method, remove its implementation (always throw an IllegalStateException or just do a noop) and finally drop the method after one or two releases since it can't really be used except for very simple apps.