[TASK] Harden \TYPO3\CMS\Extbase\Utility\DebuggerUtility

- Use strict type mode
- Use type hints whereever possible
- Use type casts according to phpstan results

Releases: master
Resolves: #88603
Change-Id: I54d3a036a7acdfe75e075269c000c03b7db3401b
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/61109


Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Daniel Goerz <daniel.goerz@posteo.de>
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: Daniel Goerz <daniel.goerz@posteo.de>