Merge `ResolvableSerializer` into `JsonSerializer`, `ResolvableDeserializer` into `JsonDeserializer`

[cowtowncoder]

(as per FasterXML/jackson3-dev#23)

So, simplify handling slightly by adding resolve(...) method from Resolvable(De)Serializer into Json(De)Serializer, add no-op implementation.
No real benefit from keeping these separate at this point.

[cowtowncoder]

Also note: while we could just remove interfaces, it may make more sense to deprecate them, at least for 3.0.