[TASK] Harden \TYPO3\CMS\Extbase\Object\Container\Container

- Use strict type mode
- Use type hints whereever possible

Releases: master
Resolves: #87606
Change-Id: I8dfdb347beca5468da1b8cb2f8a05ec7dbf4418a
Reviewed-on: https://review.typo3.org/c/59601


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Jörg Bösche <typo3@joergboesche.de>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>