Rename `GroupCoordinatorRequest` to `FindCoordinatorRequest`

[jeffwidman]

In Kafka 0.11, the GroupCoordinatorRequest / GroupCoordinatorResponse structs were renamed to FindCoordinatorRequest / FindCoordinatorResponese as part of KIP-98.

So the following need updating:

kafka-python/kafka/protocol/commit.py

Lines 244 to 251 in bb5bc1f

	class GroupCoordinatorRequest_v1(Request):
	API_KEY = 10
	API_VERSION = 1
	RESPONSE_TYPE = GroupCoordinatorResponse_v1
	SCHEMA = Schema(
	('coordinator_key', String('utf-8')),
	('coordinator_type', Int8)
	)

kafka-python/kafka/protocol/commit.py

Lines 223 to 232 in bb5bc1f

	class GroupCoordinatorResponse_v1(Response):
	API_KEY = 10
	API_VERSION = 1
	SCHEMA = Schema(
	('error_code', Int16),
	('error_message', String('utf-8')),
	('coordinator_id', Int32),
	('host', String('utf-8')),
	('port', Int32)
	)

This should be straightforward as currently the v1 version is not used by any of the code.

[jeffwidman]

See also #1641 (comment) where @dpkp noted:

I believe that v1 adds the idea of a group type. All groups I have seen are consumers, but I think Kafka Streams may use group coordination for producers or even other abstract groups. In any event, we'd need to add a parameter for group type I believe.

[jeffwidman]

Added to 2.0 milestone because that would provide an opportunity to do this rename as a backwards incompatible change...

[tvoinarovskyi]

Lets rename it and just retain the old link to the new class for some time.