Limit per IP websocket connections on wakuv2 fleets to 20

[jm-clius]

Part of investigation into waku-org/pm#23.

As mitigating factor for nodes running out of open connections, we want to limit the number of connections allowed per IP to the websocket port (8000) to 20 in the IP tables for hosts on wakuv2.prod and wakuv2,test.

[jakubgs]

Here are the changes:

• e1349d4f - conn-limit: add role for connection rate limiting
• a503ab4e - wakuv2-prod,test: set websocket conn limit at 20

Please verify the connection limit does what you want it to do.