Update to spec v1.0.0-rc.0 and BLSv4 (#1765)

## Issue Addressed

Closes #1504 
Closes #1505
Replaces #1703
Closes #1707

## Proposed Changes

* Update BLST and Milagro to versions compatible with BLSv4 spec
* Update Lighthouse to spec v1.0.0-rc.0, and update EF test vectors
* Use the v1.0.0 constants for `MainnetEthSpec`.
* Rename `InteropEthSpec` -> `V012LegacyEthSpec`
    * Change all constants to suit the mainnet `v0.12.3` specification (i.e., Medalla).
* Deprecate the `--spec` flag for the `lighthouse` binary
    * This value is now obtained from the `config_name` field of the `YamlConfig`.
        * Built in testnet YAML files have been updated.
    * Ignore the `--spec` value, if supplied, log a warning that it will be deprecated
    * `lcli` still has the spec flag, that's fine because it's dev tooling.
* Remove the `E: EthSpec` from `YamlConfig`
    * This means we need to deser the genesis `BeaconState` on-demand, but this is fine.
* Swap the old "minimal", "mainnet" strings over to the new `EthSpecId` enum.
* Always require a `CONFIG_NAME` field in `YamlConfig` (it used to have a default).

## Additional Info

Lots of breaking changes, do not merge! ~~We will likely need a Lighthouse v0.4.0 branch, and possibly a long-term v0.3.0 branch to keep Medalla alive~~.

Co-authored-by: Kirk Baird <baird.k@outlook.com>
Co-authored-by: Paul Hauner <paul@paulhauner.com>

testing/ef_tests/src/cases/bls_fast_aggregate_verify.rs

@@ -1,7 +1,7 @@
 use super::*;
 use crate::case_result::compare_result;
 use crate::cases::common::BlsCase;
-use bls::{AggregateSignature, PublicKey, PublicKeyBytes};
+use bls::{AggregateSignature, PublicKeyBytes};
 use serde_derive::Deserialize;
 use std::convert::TryInto;
 use types::Hash256;
@@ -9,6 +9,7 @@ use types::Hash256;
 #[derive(Debug, Clone, Deserialize)]
 pub struct BlsFastAggregateVerifyInput {
     pub pubkeys: Vec<PublicKeyBytes>,
+    #[serde(alias = "messages")]
     pub message: String,
     pub signature: String,
 }
@@ -28,13 +29,20 @@ impl Case for BlsFastAggregateVerify {
                 .map_err(|e| Error::FailedToParseTest(format!("{:?}", e)))?,
         );
 
-        let pubkeys = self
+        let pubkeys_result = self
             .input
             .pubkeys
             .iter()
             .map(|pkb| pkb.try_into())
-            .collect::<Result<Vec<PublicKey>, bls::Error>>()
-            .map_err(|e| Error::FailedToParseTest(format!("{:?}", e)))?;
+            .collect::<Result<Vec<_>, _>>();
+
+        let pubkeys = match pubkeys_result {
+            Ok(pubkeys) => pubkeys,
+            Err(bls::Error::InvalidInfinityPublicKey) if !self.output => {
+                return Ok(());
+            }
+            Err(e) => return Err(Error::FailedToParseTest(format!("{:?}", e))),
+        };
 
         let pubkey_refs = pubkeys.iter().collect::<Vec<_>>();