Expose Codec.typeName

[maarek]

I'd like to propose that goavro exposes the typeName *name struct through a method on the codec. I feel that this would be beneficial to the users of goavro who might be interested in the fully qualified record name, have already built the codec, and would like to save cycles parsing the schema again for it.

E.g. Use of the fqn for schema registration in the Confluent Schema Registry where the Kafka naming strategy would be against the Record Name.

[maarek]

I might have been a bit impetuous in my request and I am not sure if this needs more thought for non-record types or how that would be handled. When the typeName describes a record type and namespace, I think this could provide value.