Add support for Protobuf and JSON Schema on KafkaIO + Confluent Schema Registry

Confluent Schema Registry (CSR) 6 introduces support for other Schema types like Protobuf and JSON Schema. We should adapt KafkaIO to obtain the type of Schema and configure correctly its Deserializer and Coder.

Protobuf support
https://github.com/confluentinc/schema-registry/pull/1285
JSON Schema support
https://github.com/confluentinc/schema-registry/pull/1289