L11 compatibility

[inmanturbo]

symfony/serializer made the Symfony\Component\Serializer\Normalizer\ObjectNormalizer class final and now requires to implement some of the core methods.

We still only needed to change getSupportedTypes() so rather than copy in whole function bodies I just grabbed an instance of their ObjectNormalizer and used it for the rest.

[inmanturbo]

@freekmurze if you prefer another pattern for implementing the stubs, or want to name things differently, please feel free to edit or request changes.

[inmanturbo]

Note on the forced pushe(s):

I had squashed everything down but I though you might want to see the commits that came from running the shift, so I brought back the full history

[freekmurze]

Thank you very much!