[!!!][TASK] Indexed Search: Remove `pi1_hooks` hook

Indexed Search provided the possibility to manipulate the search
behavior via hooks with
`$GLOBALS['TYPO3_CONF_VARS']['EXTCONF']['indexed_search']['pi1_hooks']`.

There are no public extensions supporting TYPO3 v12 known using this
hooking mechanism, therefore it has been removed without replacement.

Resolves: #102937
Releases: main
Change-Id: I8236304b3af2ed89b5345ab4e2fa80e154665ff3
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/82653


Tested-by: Andreas Kienast <a.fernandez@scripting-base.de>
Reviewed-by: Andreas Kienast <a.fernandez@scripting-base.de>
Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>