Redis [NEW] default client-output-buffer-limit for monitor clients

The problem/use-case that the feature addresses

Prevent monitor clients from bringing down redis server due to unbounded memory use

Description of the feature

monitor clients are considered "normal" clients that are not limited by default. This caused our redis instance to crash due to OOM in production when someone left a monitor client running by mistake.

Monitor clients should either fall under "pubsub" class or have a different class altogether which is limited by default.

Comment From: xbasel

Monitor clients probably should be subject to some limits, they receive all commands, including read-only commands. IMO they should be subject to replica client output buffer limits (adding a new class is an overkill).