[Form] Fix "Array was modified outside object" in ResizeFormListener.

This is the second pull request for this issue. The history of this is as follows:

Original Fix was added Feb 11th under Pull Request #10232.
User's began complaining of Doctrine ArrayCollection not being updated in forms.
Revert was added Feb 15th under Pull Request #10269.

Pull Request #10269 claims to have a failing test that illustrates users concerns, but the test does not fail.
I have added failing tests to this pull request to illustrate the problems described in #10405.

I have some ideas on how to fix the users complaints regarding ArrayCollection, but I cannot recreate the problem. Some insight would be greatly appreciated.

This pull request should NOT be merged until the ArrayCollection problem has been re-created, or verified as no longer an issue.