[TASK] Properly type hint accessible mocks in tests

By adding a couple of dedicated type hints here
and there, phpstan and phpstorm understand _call()
and _set() much better.

Resolves: #96701
Releases: main, 11.5
Change-Id: Ic3f6e3f6abf897bba7144c682a64da04aa4144eb
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/73243


Tested-by: Benjamin Franzke <bfr@qbus.de>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Benjamin Franzke <bfr@qbus.de>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>