TASK: Remove usage of deprecated ``Yaml::parse`` with file path
TASK: Remove usage of deprecated ``Yaml::parse`` with file path

The symfony yaml parser deprecated handing in a file path and
instead expects the yaml content as string. As that is the same
behavior as for the PHP YAML extension the code was adapted to
read the file in all cases and pass the content to the respective
parser.

Fixes: #824

neos/flow,neos/flow,neos/flow,neos/flow