[TASK] Add simple functional tests for import/export

This patch adds some tests for a simple import and export
scenario for pages and a tt_content element.

Resolves: #55100
Releases: 6.2
Change-Id: Ia4b9a8990c7b757d25f18500def6ddd060426c2f
Reviewed-on: https://review.typo3.org/26907
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters