[TASK] Actively deprecate TypoScript TemplateService

With last non-b/w compatibility related calls to
TypoScript/TemplateService being removed, we can
now actively deprecate method usages of this class.

The deprecation has been mentioned with v12.0 in
Breaking-97816-NewTypoScriptParserInFrontend.rst
already, the patch adds trigger_error() calls and
streamlines some left over comments. Another
ReST file is added pointing to the new Request
attribute added in Frontend context.

Resolves: #99020
Related: #98503
Related: #97816
Releases: main
Change-Id: Id01f4a4cb230f632f599e06ff4efe67fd53717c3
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/76477


Tested-by: core-ci <typo3@b13.com>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>