LibJS: Add ECMA-262 section/title/URL comments almost everywhere

As mentioned on Discord earlier, we'll add these to all new functions
going forward - this is the backfill. Reasons:

- It makes you look at the spec, implementing based on MDN or V8
  behavior is a no-go
- It makes finding the various functions that are non-compliant easier,
  in the future everything should either have such a comment or, if it's
  not from the spec at all, a comment explaining why that is the case
- It makes it easier to check whether a certain abstract operation is
  implemented in LibJS, not all of them use the same name as the spec.
  E.g. RejectPromise() is Promise::reject()
- It makes it easier to reason about vm.arguments(), e.g. when the
  function has a rest parameter
- It makes it easier to see whether a certain function is from a
  proposal or Annex B

Also:

- Add arguments to all functions and abstract operations that already
  had a comment
- Fix some outdated section numbers
- Replace some ecma-international.org URLs with tc39.es

Userland/Libraries/LibJS/Runtime/GeneratorObject.cpp

@@ -29,6 +29,9 @@ GeneratorObject::GeneratorObject(GlobalObject& global_object)
 
 void GeneratorObject::initialize(GlobalObject& global_object)
 {
+    // FIXME: These should be on a separate Generator prototype object!
+    // https://tc39.es/ecma262/#sec-generator-objects
+
     auto& vm = this->vm();
     Object::initialize(global_object);
     define_native_function(vm.names.next, next);