There might be access to TSFE get_cache_timeout() prior rendering
events.
TYPO3 has a cache for timeout and won't re calculate again.
We therefore need to clear the cache if timeout would change.
That will lead to inconsistent cache information throughout a single
request. But the final cache timeout of the page will be correct. Other
parts might be longer, which probably is fine until they relate to the
events.
Relates: #10500
Use abstract classes to include necessary steps and keep actual test
cases small.
Ensure tests in CI run faster but not installing unnecessary
dependencies. But use pre installed ImageMagick.
