Changed from pure Java Schnorr signature verification to JNI libsecp256k1 gets met to 14.5k msg/sec.

I think that's good enough.

Thanks to Bitcoin Scala for the upkeep of JNI bindings. Hopefully this goes away when Foreign Function & Memory API is matured and JNI can be mothballed.

nostr:note1ckgtqhg40uy9x0pmt7a4r48fs2dkvj58g6jzl3ck95as599v0hrskacfyl