[BUGFIX] Correctly handle identical arrays in arrayDiffAssocRecursive

Add a new test to make sure that identical input arrays also deliver
an empty result as difference.

Resolves: #84067
Releases: master, 8.7, 7.6
Change-Id: Ia16ca9560094c4ae42eb69cac9e09cd4bef7dc4e
Reviewed-on: https://review.typo3.org/55923


Reviewed-by: Johannes Kasberger <johannes.kasberger@reelworx.at>
Tested-by: Johannes Kasberger <johannes.kasberger@reelworx.at>
Reviewed-by: Mathias Brodala <mbrodala@pagemachine.de>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>