Draft: info: bring lazy initialization of the categories into API

This improves the usability of the framework, because it allows to avoid calling GST_DEBUG_CATEGORY_INIT(). By avoiding calling GST_DEBUG_CATEGORY_INIT() we get rid of the "uninitialized category" error as a type, don't have to think where to put it, and in the end it allows us to write less code. At a first impression it may seem that the lazy initialization of the category has some micro performance cost, but in fact it can also be seen the way around: if GST_DEBUG is not set, the category won't be initialized at all, that is a micro performance win.