Faster attestation production (#838)

* Start adding interop genesis state to lcli

* Use more efficient method to generate genesis state

* Remove duplicate int_to_bytes32

* Add lcli command to change state genesis time

* Add option to allow VC to start with unsynced BN

* Set VC to do parallel key loading

* Don't default to dummy eth1 backend

* Add endpoint to dump operation pool

* Add metrics for op pool

* Remove state clone for slot notifier

* Add mem size approximation for tree hash cache

* Avoid cloning tree hash when getting head

* Avoid cloning tree hash when getting head

* Add working arena-based cached tree hash

* Add another benchmark

* Add pre-allocation for caches

* Make cache nullable

* Fix bugs in cache tree hash

* Add validator tree hash optimization

* Optimize hash_concat

* Make hash32_concat return fixed-len array

* Fix failing API tests

* Add new beacon state cache struct

* Add validator-specific cache

* Separate list and values arenas

* Add parallel validator registry hashing

* Remove MultiTreeHashCache

* Remove cached tree hash macro

* Fix failing tree hash test

* Address Michael's comments

* Add CachedTreeHash impl for ef tests

* Fix messy merge conflict

* Optimize attestation production

* Add first basic optimizations

* Fix SlotOutOfBounds error

* Resolved missed merge conflicts

* Fix another missed merge conflict

* Fix more merge conflict issues

* Add `StateSkipConfig`

* Fix test compile errors

* Add failing test

* Fix bug, make tests pass

* Add comment

* Delete unused function

* Replace deleted comment

eth2/types/src/beacon_state.rs

@@ -854,7 +854,7 @@ impl<T: EthSpec> BeaconState<T> {
 
     /// Returns the cache for some `RelativeEpoch`. Returns an error if the cache has not been
     /// initialized.
-    fn committee_cache(&self, relative_epoch: RelativeEpoch) -> Result<&CommitteeCache, Error> {
+    pub fn committee_cache(&self, relative_epoch: RelativeEpoch) -> Result<&CommitteeCache, Error> {
         let cache = &self.committee_caches[Self::committee_cache_index(relative_epoch)];
 
         if cache.is_initialized_at(relative_epoch.into_epoch(self.current_epoch())) {