[TASK] Streamline request handling in frontend functional tests

see https://github.com/TYPO3/testing-framework/pull/328

composer req --dev typo3/testing-framework:^6.15.3

Besides that, corresponding test cases for shortcut redirects
were extended to make the actual behavior more explicit there.

Resolves: #96818
Releases: 11.5
Change-Id: Ia0ffaaf0a6c93a05513f73bec5a5e5fb75b9eac7
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/73387


Tested-by: core-ci <typo3@b13.com>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>