[TASK] Store legacy deprecation file in generic log folder

The deprecation log file that was used prior to v9.0, was previously
stored in typo3conf/deprecation_* which is still used for extensions
still using the old API, is now put into var/log/ where all other
log files reside.

For installations using the environment concept with
"$_ENV['TYPO3_PATH_APP']" - e.g. all installations in composer mode -
the file is now created at that place, for installations having
everything in the public web root, the file is now in
"typo3temp/var/log/deprecation_...log".

Resolves: #85198
Releases: master
Change-Id: I0fc23d9fec6cfa45241c041f64333deb90d44950
Reviewed-on: https://review.typo3.org/57160


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>