Experimental modern core (RESP3 with possible Cluster and/or Sentinel support)

[ptaoussanis]

Would like to commit a couple days to at least check on the current status of the relevant protocols, and get a rough cost estimate.

To help me gauge demand, please 👍 this issue if you'd make use of Cluster and/or Sentinel support.

[ptaoussanis]

• Current RESP3 spec: https://github.com/redis/redis-specifications/blob/master/protocol/RESP3.md
• Cluster docs: https://redis.io/docs/reference/cluster-spec/
• Sentinel docs: https://redis.io/docs/reference/sentinel-clients/
• Previous Cluster issue: https://github.com/ptaoussanis/carmine/issues/76

[ptaoussanis]

First experiments looking promising, going to proceed with this work as I have time.

Closing, moved related tasks to v4 project.