Added deterministic keypair generation.

- The Account Manager has a new subcommand, allowing generation of deterministic keys given a particular validator index.
 - Split functionality in generate_deterministic_keypair function
 - Fixed up READMEs to reflect new functionality & correct naming.

eth2/types/src/test_utils/generate_deterministic_keypairs.rs

@@ -18,13 +18,17 @@ pub fn generate_deterministic_keypairs(validator_count: usize) -> Vec<Keypair> {
     let keypairs: Vec<Keypair> = (0..validator_count)
         .collect::<Vec<usize>>()
         .par_iter()
-        .map(|&i| {
-            let secret = int_to_bytes48(i as u64 + 1000);
-            let sk = SecretKey::from_bytes(&secret).unwrap();
-            let pk = PublicKey::from_secret_key(&sk);
-            Keypair { sk, pk }
-        })
+        .map(|&i| generate_deterministic_keypair(i))
         .collect();
-
     keypairs
 }
+
+/// Generates a single deterministic keypair, where the secret key is `validator_index`.
+///
+/// This is used for testing only, and not to be used in production!
+pub fn generate_deterministic_keypair(validator_index: usize) -> Keypair {
+    let secret = int_to_bytes48(validator_index as u64 + 1000);
+    let sk = SecretKey::from_bytes(&secret).unwrap();
+    let pk = PublicKey::from_secret_key(&sk);
+    Keypair { sk, pk }
+}

eth2/types/src/test_utils/mod.rs

@@ -16,6 +16,7 @@ mod testing_transfer_builder;
 mod testing_voluntary_exit_builder;
 
 pub use generate_deterministic_keypairs::generate_deterministic_keypairs;
+pub use generate_deterministic_keypairs::generate_deterministic_keypair;
 pub use keypairs_file::KeypairsFile;
 pub use rand::{prng::XorShiftRng, SeedableRng};
 pub use serde_utils::{fork_from_hex_str, u8_from_hex_str};