Move PublicKey to store uncompressed bytes.

This is an optimisation that allows for faster hashing of a public key,
however it adds a penalty to SSZ encoding because we need to go
decompressed -> PublicKey -> compressed.

The spec presently uses compressed bytes to store public keys, however
I'm hoping it will change.

eth2/utils/bls/src/aggregate_public_key.rs

@@ -14,7 +14,7 @@ impl AggregatePublicKey {
     }
 
     pub fn add(&mut self, public_key: &PublicKey) {
-        self.0.add(public_key.as_raw())
+        self.0.add(&public_key.as_raw())
     }
 
     /// Returns the underlying signature.