[!!!][TASK] Remove last usages of $GLOBALS[T3_VAR]

The global state array "T3_VAR" for keeping some legacy
functionality has been removed.

It is not in used by TYPO3 Core anymore, the last occurrence
for "injecting" some data into Indexed Search indexing
has been removed, as SingletonInterface, hooks and the possibility
to provide ones' own indexer for custom download extensions
should be used instead.

Resolves: #88660
Releases: master
Change-Id: I5a587271983c6bb4ae6709c0140e818c4c1eb572
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/61197


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Steffen Frese <steffenf14@gmail.com>
Tested-by: Jörg Bösche <typo3@joergboesche.de>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Steffen Frese <steffenf14@gmail.com>
Reviewed-by: Jörg Bösche <typo3@joergboesche.de>
Reviewed-by: Benni Mack <benni@typo3.org>