Allow configuration of JSON serialization for a given property in the model

[ajcvickers]

This should allow:

• Database providers and plugins (e.g. for spatial Support spatial types in JSON columns #28811) to provide their own serialization for values.
• Users to override the serialization on a given property or all properties in the same way as can be done with value converters.

[maumar]

dupe of #28043

[ajcvickers]

Not a duplicate of #28043. This is about providers changing the content that is actually serialized, not the way it is serialized.