Altair consensus changes and refactors (#2279)

## Proposed Changes

Implement the consensus changes necessary for the upcoming Altair hard fork.

## Additional Info

This is quite a heavy refactor, with pivotal types like the `BeaconState` and `BeaconBlock` changing from structs to enums. This ripples through the whole codebase with field accesses changing to methods, e.g. `state.slot` => `state.slot()`.


Co-authored-by: realbigsean <seananderson33@gmail.com>

beacon_node/network/src/beacon_processor/tests.rs

@@ -3,10 +3,10 @@
 
 use crate::beacon_processor::*;
 use crate::{service::NetworkMessage, sync::SyncMessage};
-use beacon_chain::{
-    test_utils::{AttestationStrategy, BeaconChainHarness, BlockStrategy, EphemeralHarnessType},
-    BeaconChain, MAXIMUM_GOSSIP_CLOCK_DISPARITY,
+use beacon_chain::test_utils::{
+    AttestationStrategy, BeaconChainHarness, BlockStrategy, EphemeralHarnessType,
 };
+use beacon_chain::{BeaconChain, MAXIMUM_GOSSIP_CLOCK_DISPARITY};
 use discv5::enr::{CombinedKey, EnrBuilder};
 use environment::{null_logger, Environment, EnvironmentBuilder};
 use eth2_libp2p::{rpc::methods::MetaData, types::EnrBitfield, MessageId, NetworkGlobals, PeerId};
@@ -66,6 +66,7 @@ impl TestRig {
     pub fn new(chain_length: u64) -> Self {
         let mut harness = BeaconChainHarness::new(
             MainnetEthSpec,
+            None,
             generate_deterministic_keypairs(VALIDATOR_COUNT),
         );