[!!!][TASK] Remove TypoScript option page.includeCSS/includeCSSLibs.import

The option to use the @import syntax in TypoScript
"page.includeCSS" and "page.includeCSSLibs"
(.import subproperty per CSS file) will not work anymore.

Resolves: #96118
Related: #95349
Releases: master
Change-Id: Ibcbcf091eca00d061cc79b551f87995ddf47c1a0
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/72338


Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>