Enable Redis client cache

[davies]

What would you like to be added:

We can enable the redis client cache by command options, which could be useful for readonly workload.

Why is this needed:

Faster is always good.

[davies]

After looking into the details of client cache, it's complicated, so we move this out of 1.0 milestone.

[bigzed]

I recently was trying out juicefs with a Redis instance that had a network latency of over 20ms. I was wondering whether Redis client caching is part of any foreseeable future milestones?

[rueian]

Hi @davies,

Would you consider using https://github.com/redis/rueidis? It has the client cache implemented.