[!!!][TASK] Remove Indexed Search option searchSkipExtendToSubpagesChecking

The option searchSkipExtendToSubpagesChecking in Indexed
search is removed in favor of using a better functionality
of getTreeList() which has been implemented in TYPO3 Core,
considering "extendToSubpages" at any times.

Resolves: #97530
Releases: main
Change-Id: Iabe82f2846aaa6d586ef30c0128e957b24531562
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/74377


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