Move verify_share to return batch-verifiable statements

While the previous construction achieved n/2 average detection,
this will run in log2(n). Unfortunately, the need to keep entropy
around (or take in an RNG here) remains.

crypto/frost/src/curve/mod.rs

@@ -1,7 +1,7 @@
 use core::ops::Deref;
 use std::io::{self, Read};
 
-use rand::{RngCore, CryptoRng};
+use rand_core::{RngCore, CryptoRng};
 
 use zeroize::{Zeroize, Zeroizing};
 use subtle::ConstantTimeEq;