[Serializer] Fatal error in denormalizeObject for Normalizers that do not implement DenormalizerInterface

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | 7971
| License       | MIT
| Doc PR        | 

If there is a list of Normalizers, and only some of them implement DenormalizerInterface, then a call to deserialize() can result in a fatal error. 

This is because denormalizeObject does not check that the Normalizer implements DenormalizerInterface before calling supportsDenormalization on it.