[BUGFIX] Make environment check standalone

The system environment check is supposed to be useable standalone
without any TYPO3 internal requirements.

Move all checks which require a fully set up TYPO3 installation
into a separate class and use it where necessary.

Resolves: #69495
Releases: master
Change-Id: I9f78f8c03a28d18a6daa326b321db721800e7599
Reviewed-on: https://review.typo3.org/42861


Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Andreas Wolf <andreas.wolf@typo3.org>
Tested-by: Andreas Wolf <andreas.wolf@typo3.org>