Introduce "schematic" normalizers

We've long desired the ability for core to easily produce a "correct" schema for a given entity type/bundle. The concept of "schematic" normalizers will get us closer.

While this issue/concept was originally blocked by an inability to cache the outcome of a "supports" query on a normalizer, that was fixed in #3252872: Use CacheableSupportsMethodInterface for performance improvement in normalizers thanks in large part to changes upstream in Symfony.

Proposed Solution (originally authored by @gabesullice):

Add a SchematicNormalizerInterface with a ::getNormalizationSchema() method.

Initial thoughts on a method signature:

• $type is a supported interface or class.
• $format is the encoding format.
• $refinements is a parameter bag of anything that is required to return a correct schema. For example, ResourceObjectNormalizer::getNormalizationSchema() would need $refinements->get('resource_type'). Best practice would be for refinements to be documented on the method and then asserted in the method. It's imperfect, but the best I can think of.

I think under this system, every normalizer would be required to return a complete schema. Meaning that the JsonApiDocumentTopLevelNormalizer would be responsible for returning a schema that included schema for any child resource object(s). Alternatively, we could allow normalizers to return placeholder objects and resolve them separately. That might end up as an over-engineered solution though.

Finally, I think that we would put this method on the Serializer service so that normalizers will not need to specifically know which child normalizer services will be applied.