The @import syntax has been introduced with TYPO3 v9.
With the TypoScript parser rewrite in v12, some last
todos have been ruled out in this area.
There are some good reasons to finally phase out
`<INCLUDE_TYPOSCRIPT:`, the deprecation ReST gives
further information.
The patch adds an active trigger_error() when the
parser hits a `<INCLUDE_TYPOSCRIPT:` statement and
marks all related handling code as deprecated.

Resolves: #105171
Related: #96614
Related: #101807
Related: #97816
Related: #103439
Releases: main
Change-Id: Ic5b25afc99e16054016beac57c1f115f11b015c8
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/86386


Reviewed-by: Simon Schaufelberger <simonschaufi+typo3@gmail.com>
Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>