[TASK] Skip test for Yaml PHP extension if not loaded

Resolves: #83861
Releases: master, 8.7
Change-Id: I235e5e37405b264ce071c8d6ecb2b0c13f64357c
Reviewed-on: https://review.typo3.org/55673


Reviewed-by: Helmut Hummel <typo3@helhum.io>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Stefan Neufeind <typo3.neufeind@speedpartner.de>
Tested-by: Stefan Neufeind <typo3.neufeind@speedpartner.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>