Switch to ring for hkdf (#1134)

* Switch to ring for hkdf

* Remove comments

* Make some keystore tests release only

eth2/utils/eth2_keystore/tests/eip2335_vectors.rs

@@ -3,6 +3,7 @@
 //! https://eips.ethereum.org/EIPS/eip-2335
 
 #![cfg(test)]
+#![cfg(not(debug_assertions))]
 
 use eth2_keystore::{Keystore, Uuid};
 

eth2/utils/eth2_keystore/tests/json.rs

@@ -340,6 +340,7 @@ fn bad_version() {
 }
 
 #[test]
+#[cfg(not(debug_assertions))]
 fn json_bad_checksum() {
     let vector = r#"
             {

eth2/utils/eth2_keystore/tests/tests.rs

@@ -1,4 +1,5 @@
 #![cfg(test)]
+#![cfg(not(debug_assertions))]
 
 use bls::Keypair;
 use eth2_keystore::{Error, Keystore, KeystoreBuilder};