fix(ngClass): add/remove classes which are properties of Object.prototype

Previously, ngClass and ngAnimate would track the status of classes using an ordinary object.
This causes problems when class names match names of properties in Object.prototype, including
non-standard Object.prototype properties such as 'watch' and 'unwatch' in Firefox. Because of
this shadowing, ngClass and ngAnimate were unable to correctly determine the changed status
of these classes.

In orderto accomodate this patch, some changes have been necessary elsewhere in the codebase,
in order to facilitate iterating, comparingand copying objects with a null prototype, or which
shadow the `hasOwnProperty` method

Summary:

- fast paths for various internal functions when createMap() is used
- Make createMap() safe for internal functions like copy/equals/forEach
- Use createMap() in more places to avoid needing hasOwnProperty()

R=@matsko

Closes #11813
Closes #11814