ComponentRegistry should probably be its own class

[vulppine]

Right now, there are a few systems in Space Station 14 that leverage component registries[1]. This, however, requires them to re-implement the method used to load components into entities, as usually these component registries are embedded into prototypes.

What would be nice is that if a user wanted to load components into an entity from another prototype source, they could just use a component registry within that prototype, and then place the components into that entity, rather than reimplement the method used to load components from a registry into an entity.

[1]: Content.Server/Jobs/AddComponentSpecial.cs, Content.Shared/Traits/TraitPrototype.cs & Content.Server/Traits/TraitSystem.cs