Remove shard list querying from Kinesis consumer constructor

Currently FlinkKinesisConsumer is querying for the whole list of shards in the constructor, forcing the client to be able to access Kinesis as well. This is also a drawback for handling Kinesis-side resharding, since we'd want all shard listing / shard-to-task assigning / shard end (result of resharding) handling logic to be capable of being independently done within task life cycle methods, with defined and definite results.