In `wp_get_object_terms()`, before returning terms (and before running them through the 'wp_get_object_terms' filter) - run them through `$terms = array_values( array_unique( $terms, SORT_REGULAR ) )`. 

There will be "dupes" when the function is called with `'fields' => 'all_with_object_id'`, but the objects will actually be unique due to the `object_id` addition, so they shouldn't be filtered out. 

Adds unit tests. All other unit tests pass.

Fixes #11003.


git-svn-id: https://develop.svn.wordpress.org/trunk@28583 602fd350-edb4-49c9-b593-d223f7449a82