Support handshake v0

[starbelly]

Currently this plugin does not support handshake v0. It supports sasl auth prior to the handshake being introduced in kafka protocol, we currently call this module brod_gssapi_v0, which is wrong, it should perhaps be called brod_gssapi_legacy.

brod_gssapi_v1 which supports handshake version 1, should be renamed to something that doesn't paint it into a v1 corner. In other words, it should be able to work with v0 or v1 handshakes.

Reference:

https://github.com/kafka4beam/kafka_protocol/blob/713a00e30a5f7ab0d19558c502a7e5cc5b0bfa68/src/kpro_sasl.erl#L75

https://kafka.apache.org/protocol.html#sasl_handshake

https://cwiki.apache.org/confluence/display/KAFKA/KIP-43%3A+Kafka+SASL+enhancements