[TASK] Use new templating strategy in ext:impexp

Straight implementation of the new backend
templating strategy in ext:impexp.

Resolves: #96773
Related: #96730
Releases: main
Change-Id: If69320a4e1850e5c0c22682e8d46837d891ea8e8
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/73336


Tested-by: core-ci <typo3@b13.com>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Nikita Hovratov <nikita.h@live.de>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Nikita Hovratov <nikita.h@live.de>
Reviewed-by: Benni Mack <benni@typo3.org>