BM-2107: env variable to set a redis memory cap for queueing more prove segments

[austinabell]

Sets an environment variable such that when above that redis memory usage it will warn in logs and pause execution and the queueing of more segments until the memory level below the threshold again. Aims to avoid OOM issues with redis without dealing with eviction issues.

TODO:

• Consider setting a value for this in wizard based on host machine's available memory
• Probably rename env vars, being redis based might be confusing given switch to valkey