[BUG] WATCH can consume large amounts of memory and bypasses OOM

[madolson]

From @enjoy-binbin

WATCH is not flag with denyoom, so we can keep watching keys and consume the memory.

Also true of SUBSCRIBE.

[madolson]

I think the consensus was that we don't think this is critical for Valkey 9.1, we should do it for 10.0. We don't think adding an OOM error for the WATCH and SUBSCRIBE make sense, but evicting clients by using more memory with #3362 makes more sense. The details of how memory will be tracked is tbd.

@enjoy-binbin I saw you dropped, does this solve your use case?

[enjoy-binbin]

So we will rely on the clients eviction (maxmemory-clients) to migrate this issue. So #3362 should be able to close it, i added it to the 10.0 project, we can review it later.