[TASK] Harden \TYPO3\CMS\Extbase\Service\EnvironmentService

- Use strict type mode
- Use type hints whereever possible

Releases: master
Resolves: #87597
Change-Id: Ic4cfb5512f49b3e20fa16c782301b8dcb2ba5dec
Reviewed-on: https://review.typo3.org/59592


Reviewed-by: Mona Muzaffar <mona.muzaffar@gmx.de>
Tested-by: Mona Muzaffar <mona.muzaffar@gmx.de>
Reviewed-by: André Schließer <andy.schliesser@gmail.com>
Tested-by: André Schließer <andy.schliesser@gmail.com>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: TYPO3com <noreply@typo3.com>
Reviewed-by: Felix Döring <Felix.Doering@3m5.de>
Tested-by: Felix Döring <Felix.Doering@3m5.de>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>