[FEATURE] Allow site in TypoScript getText

A new key "site" for TypoScript "getText" has been introduced
which allows accessing site configuration.

Resolves: #86422
Releases: master
Change-Id: Id0efae08445b8890021fb2b68a88c4ac8db5a6fa
Reviewed-on: https://review.typo3.org/58434


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Jörg Bösche <typo3@joergboesche.de>
Tested-by: Jörg Bösche <typo3@joergboesche.de>
Reviewed-by: Tobi Kretschmann <tobi@tobishome.de>
Tested-by: Tobi Kretschmann <tobi@tobishome.de>
Reviewed-by: Frank Naegler <frank.naegler@typo3.org>
Tested-by: Frank Naegler <frank.naegler@typo3.org>