[BUGFIX] Respect "sectionIndex" setting in section menus

The content element "Section index of subpages from selected pages"
now also respects the setting "Show in Section Menus".

Resolves: #100262
Releases: main, 11.5
Change-Id: I92c52cd48c0732410ded00c508fdd16633d67035
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/78299


Tested-by: core-ci <typo3@b13.com>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>