[TASK] Avoid implicitly nullable class method parameter in tests

With PHP 8.4 marking method parameter implicitly nullable
is depreacted and will emit a `E_DEPRECATED` warning. One
recommended way to resolve this, is making it explicitly
nullable using the `?` nullable operator. [1]

In cases, where are implicitly nullable parameter exists
before not-nullable parameters in a method or constructor,
making it explicitly nullable will emit a

  Optional parameter <paramname> declared before required
  parameter <paramname> is implicitly treated as a required
  parameter

since PHP 8.0 [2].

This change adds the `?` nullable operator [1] and removes
the null default value when one or more non-optional argument
follows [2] to mitigate both issues.

Note that the second case is a edge case in this change.

This prepares the way towards PHP 8.4 compatibility and
unifies towards using `?` nullable operator over union
null type when possible.

[1] https://php.watch/versions/8.4/implicitly-marking-parameter-type-nullable-deprecated
[2] https://php.watch/versions/8.0/deprecate-required-param-after-optional

Resolves: #104182
Releases: main, 12.4, 11.5
Change-Id: I68362a89458117eca4f0488c67a0b9ed17e7b929
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/84859


Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Oliver Klee <typo3-coding@oliverklee.de>