[TASK] Drop deprecated testing-framework method usages

Functional test case methods getFrontendResponse() and
getFrontendResult() have been deprecated a while ago
but their core usages have not been adapted. Do this
now by switching to their younger counterparts.

Change-Id: Ica1a6625a29b9d35189f2c9fce29da52f121d280
Resolves: #92845
Releases: master, 10.4
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/66635


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>