feat: Validation mechanism to limit "free traffic" on the network

[chair28980]

This tracks the work to define and implement a relay validator that allows nodes to limit the amount of bandwidth they're willing to allocate for routing "free traffic". In this case, "free traffic" would be Waku messages with no RLN proofs.

specification: @vpavlin

Priority: Critical for launch

[chair28980]

https://github.com/waku-org/research/issues/3

@danisharora099 @weboko

Per the research issue, can y'all verify if this is required for JSWaku and assign ownership as necessary. Thank you!

[fryorcraken]

This has been descoped from gen 0 and should not be priority