Add support for up to version 4 List Groups API

[prestona]

This adds support for versions 1 through 4 of the ListGroups API.

A compromise for backwards compatibility is the addition of a new GroupsData field to the list groups response, leaving the existing Groups field unchanged:

type ListGroupsResponse struct {
	Version      int16
	ThrottleTime int32
	Err          KError
	Groups       map[string]string    // <- existing field group_id -> protocol_type
	GroupsData   map[string]GroupData // <- new field added by this PR
}

type GroupData struct {
	GroupState string
}

A more faithful, yet incompatible, rendering for this part of the Kafka protocol (see below) would have been to change the type of the existing Groups field to be a map of string (group ID) to a struct with fields for "protocol_type" and "group_state".

ListGroups Response (Version: 4) => throttle_time_ms error_code [groups] TAG_BUFFER 
  throttle_time_ms => INT32
  error_code => INT16
  groups => group_id protocol_type group_state TAG_BUFFER 
    group_id => COMPACT_STRING
    protocol_type => COMPACT_STRING
    group_state => COMPACT_STRING

Ideally, if any further fields are added into the "groups" section of the protocol, they will be added into the GroupsData field of the ListGroupsResponse struct.

Contributes-to: #2408

[dnwe]

Thanks! Changes look good to me, I've rebased on main and just letting the tests run through now