modelset chunk size should be configurable

[filipecosta90]

Given https://github.com/redis/redis/blob/unstable/redis.conf#L1854 there might be cases in which we have a Redis instance with a max string size of 1,2,10mb....
The hotfix that added modelset chunking to the client ( https://github.com/RedisAI/redisai-py/pull/35/files ) enforces a chunk size of 512mb. We should address this ( or at least be aware of the limitations/issues that can arise from the current config )

[DvirDukhan]

@filipecosta90 can we get this value from CONFIG GET command?

[filipecosta90]

@filipecosta90 can we get this value from CONFIG GET command?

yes :

127.0.0.1:6379> config get proto-max-bulk-len
1) "proto-max-bulk-len"
2) "536870912"