fix(ngRepeat): do not sort object keys alphabetically

BREAKING CHANGE:

Previously, the order of items when using ngRepeat to iterate
over object properties was guaranteed to be consistent by sorting the
keys into alphabetic order.

Now, the order of the items is browser dependent based on the order returned
from iterating over the object using the `for key in obj` syntax.

It seems that browsers generally follow the strategy of providing
keys in the order in which they were defined, although there are exceptions
when keys are deleted and reinstated. See
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/delete#Cross-browser_issues

The best approach is to convert Objects into Arrays by a filter such as
https://github.com/petebacondarwin/angular-toArrayFilter
or some other mechanism, and then sort them manually in the order you need.

Closes #6210
Closes #10538