[TASK] Upgrade phpunit 6 to 7

Our dependencies are meanwhile phpunit 7 compatible
so we can upgrade to it now. Some minor changes in
the tests are needed along the way.

composer update --with-dependencies \
	typo3/testing-framework \
	phpunit/phpunit \
	codeception/codeception
composer require --dev fiunchinho/phpunit-randomizer:^4.0

Change-Id: I161d43a9063b048085f27c5a7ae9249df8d6a2a9
Resolves: #84958
Releases: master
Reviewed-on: https://review.typo3.org/56900


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Tymoteusz Motylewski <t.motylewski@gmail.com>
Tested-by: Tymoteusz Motylewski <t.motylewski@gmail.com>