support cluster configuration with dfly_bench

[romange]

dfly_bench covers lots of load-testing use-cases but it still does not support the cluster mode.

The goal of this task is to provide cluster support by sending cluster discovery request if the protocol flag FLAGS_P is RESP.

In that case we should create threads x c connections per shard and drive all of them to completion

[romange]

Most cluster support is done, what's missing is handling MOVED responses by moving slots ownership from one Driver instance to another. It is possible to simulate this locally using cluster_mgr.py
Driver::ParseRESP() is where we identify MOVED but currently drivers are not aware of each other, so they can not communicate between them. Note that each thread manages its own driver set via TLocalClient.