[TASK] Deprecate TYPO3_OS constant

The TYPO3_OS constant is deprecated with
the introduction of Environment API.

Resolves: #85597
Releases: master
Change-Id: Ie0f844d2d024f2a3f6acdf5af24debead6ba836b
Reviewed-on: https://review.typo3.org/57632


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Mathias Schreiber <mathias.schreiber@typo3.com>
Tested-by: Mathias Schreiber <mathias.schreiber@typo3.com>
Reviewed-by: Daniel Goerz <ervaude@gmail.com>
Tested-by: Daniel Goerz <ervaude@gmail.com>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>