Bake noteguard directly into the relay

[jb55]

I was thinking about making a proxy mode for noteguard:

• Proxy mode noteguard#9

A simpler approach for notepush is to simply use noteguard as a library to do filtering directly within the relay on incoming notes.

The main reason we would want to do this is so that people can't DoS the relay by spamming it directly with notes, which could trigger lots of remote mutelist lookups.