[secp256k1] add schnorr verify jni binding

Summary: schnorr jni binding that will allow jvm support

Test Plan:
use the test vector data from
https://github.com/sipa/bips/blob/bip-schnorr/bip-schnorr/test-vectors.csv

Reviewers: O1 Bitcoin ABC, #bitcoin_abc, deadalnix, jasonbcox

Reviewed By: O1 Bitcoin ABC, #bitcoin_abc, jasonbcox

Subscribers: jasonbcox, schancel

Differential Revision: https://reviews.bitcoinabc.org/D2745