[TASK] Stabilize ac tests again

We're in the process of establishing a new
core CI. This has more power and is better
optimized.
The resulting runtime changes reveal various
flaky acceptance tests. Most have been
problematic before already, but not as bad.
The patch adds various guards to acceptance
tests to reduce flakiness.

Resolves: #102363
Releases: main, 12.4, 11.5
Change-Id: Iff2c79411b39fffe659c78a8e889f8a804939bc4
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/81722


Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>