Use `futures` to parallelize calls to `_send_request_to_node()`

This allows queries that need to go to multiple brokers to be run in parallel.

Now that the old zookeeper consumer has been completely deprecated/removed, these are no longer the "new consumer configs" but rather simply the "consumer configs"

1. Remove unused variable: `partitions_for_topic`
2. No need to cast to list as `sorted()` already returns a list
3. Using `enumerate()` is cleaner than `range(len())` and handles assigning
`member`