Symfony YAML does not parse all YAML

While trying to add more tests for more specs from these sources:

- https://github.com/Mermade/openapi3-examples/tree/master/resources
- https://github.com/Nexmo/api-specification/tree/master/definitions
- https://github.com/APIs-guru/openapi-directory

I found that symfony YAML fails on a lot of these.
We either need an alternative YAML parser or improve symfony YAML to not fail.

- https://github.com/yaml/yaml-test-suite
- https://github.com/symfony/symfony/issues/27965