[TASK] Drop remaining _GP and getIndpEnv in ContentElement/ElementHistoryController

Also pass around request object internally instead of storing it as property.

Change-Id: Idac5aaab8817225451cf59d2e677218033e6b2fb
Resolves: #84388
Releases: master
Reviewed-on: https://review.typo3.org/56283


Tested-by: TYPO3com <no-reply@typo3.com>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>