[core] finish adding inherited members/attrs/events for a class

[thepassle]

Currently it only does fields, finish attrs/events as well

Also make sure to not have duplicates, e.g.: if a method is already present in the class's members, it means the class is overriding it

example:

class Foo extends Super {
  someMethod(){}
}

class Super extends HTMLElement {
  someMethod(){}
}

someMethod should only be in the output classdoc for Foo once