fix($controller): remove instantiating controllers defined on window

This also removes the likewise deprecated `$controllerProvider.allowGlobals()` method.

Closes #15349
Closes #15762

BREAKING CHANGE:

The option to instantiate controllers from constructors on the global `window` object
has been removed. Likewise, the deprecated `$controllerProvider.allowGlobals()`
method that could enable this behavior, has been removed.

This behavior had been deprecated since AngularJS v1.3.0, because polluting the global scope
is bad. To migrate, remove the call to $controllerProvider.allowGlobals() in the config, and
register your controller via the Module API or the $controllerProvider, e.g.

```
angular.module('myModule', []).controller('myController', function() {...});

angular.module('myModule', []).config(function($controllerProvider) {
  $controllerProvider.register('myController', function() {...});
});

```