Should allow deserialization of java.time types via opaque JsonToken.VALUE_EMBEDDED_OBJECT

[cowtowncoder]

Jackson 2.12 added a safety feature #2683 which will block attempts to read/write java.time.* values if no explicit value serializer/deserializer found (which implies Java 8 date/time module is not registered).

While this makes sense on its own, it does have the downside that it is not possible to pass such values as opaque/embedded/POJO values, to use via ObjectMapper.convertValue() for example, or store in JsonNode.
Such use can be useful for some processing pipelines, and seems like it should be allowed.

[cowtowncoder]

Note to self: I think this should go in 2.13 to reduce likelihood of a regression in 2.12 from change to deserializers.

[cowtowncoder]

Should be fixed now by change to UnsupportedTypeDeserializer which allows such operation (could consider adding similar general handling to other base deserializers maybe).