AVRO-3947: [Java] Support subclasses in custom LogicalType Conversions

[tmoschou]

What is the purpose of the change

Currently GenericData.resolveUnion(schema, datum) will throw an AvroRuntimeException if datum is a subclass (or any instance) of the target type of an applicable logical type Conversion. For instance

• "ip-address" logical type string converter to/from java.net.InetAddress (with Inet4Address, Inet6Address as subclasses)
• "json" logical type string conversion to/from Jackson's JsonNode (with ObjectNode, ArrayNode, etc as subclasses)

This PR fixes AVRO-3947.

Verifying this change

A unit test was added to validate that GenericData.resolveUnion(schema, datum) behaves as intended.

Documentation

• Does this pull request introduce a new feature? no
• If yes, how is the feature documented? not applicable

[tmoschou]

Okay, I have also extended the fix to handling other code like GenericDatumWriter by fixing GenericData.getConversionByClass(datumClass, logicalType) which also failed when writing datums with type Class<? extends T> rather than Class<T>. We didn't notice it before as we are using our own custom writer. The only other usage I can see potentially being a problem is GenericData.getConversionByClass(class) whose usage as far as I can tell is only used for schema inference in Reflect/Protobuf - In that case I think it makes sense to keep the old behaviour, although some might have knowledge that values of a specific logical type is always of a particular subclass, although they can always use @AvroSchema for Reflect data. E.g.

class MyRecord {
  String foo;
  
  @AvroSchema("{\"type\":\"string\",\"logical-type\":\"json\"")
  ObjectNode metadata;
}

where conversion is defined for JsonNode (JsonNode.class.isAssignableFrom(ObjectNode.class))