Update VC and BN APIs for naive aggregation (#950)

* Refactor `Attestation` production

* Add constant

* Start refactor for aggregation

* Return early when no attesting validators

* Refactor into individual functions

* Tidy, add comments

* Add first draft of NaiveAggregationPool

* Further progress on naive aggregation pool

* Fix compile errors in VC

* Change locking logic for naive pool

* Introduce AttesationType

* Add pruning, comments

* Add MAX_ATTESTATIONS_PER_SLOT restriction

* Add pruning based on slot

* Update BN for new aggregation fns

* Fix test compile errors

* Fix failing rest_api test

* Move SignedAggregateAndProof into own file

* Update docs, fix warning

* Tidy some formatting in validator API

* Remove T::default_spec from signing

* Fix failing rest test

* Tidy

* Add test, fix bug

* Improve naive pool tests

* Add max attestations test

* Revert changes to the op_pool

* Refactor timer

beacon_node/beacon_chain/tests/store_tests.rs

@@ -6,7 +6,7 @@ extern crate lazy_static;
 use beacon_chain::test_utils::{
     AttestationStrategy, BeaconChainHarness, BlockStrategy, DiskHarnessType,
 };
-use beacon_chain::AttestationProcessingOutcome;
+use beacon_chain::{AttestationProcessingOutcome, AttestationType};
 use rand::Rng;
 use sloggers::{null::NullLoggerBuilder, Build};
 use std::sync::Arc;
@@ -306,7 +306,7 @@ fn epoch_boundary_state_attestation_processing() {
             .epoch;
         let res = harness
             .chain
-            .process_attestation_internal(attestation.clone(), Some(true));
+            .process_attestation_internal(attestation.clone(), AttestationType::Aggregated);
 
         let current_epoch = harness.chain.epoch().expect("should get epoch");
         let attestation_epoch = attestation.data.target.epoch;