Optimizations, disable val client sync check & additional lcli tools (#834)

* 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

* Fix failing API tests

* Address Michael's comments

* Add HashMap::from_par_iter

eth2/operation_pool/src/lib.rs

@@ -284,6 +284,16 @@ impl<T: EthSpec> OperationPool<T> {
         });
     }
 
+    /// Total number of attester slashings in the pool.
+    pub fn num_attester_slashings(&self) -> usize {
+        self.attester_slashings.read().len()
+    }
+
+    /// Total number of proposer slashings in the pool.
+    pub fn num_proposer_slashings(&self) -> usize {
+        self.proposer_slashings.read().len()
+    }
+
     /// Insert a voluntary exit, validating it almost-entirely (future exits are permitted).
     pub fn insert_voluntary_exit(
         &self,
@@ -327,6 +337,11 @@ impl<T: EthSpec> OperationPool<T> {
         self.prune_attester_slashings(finalized_state, spec);
         self.prune_voluntary_exits(finalized_state);
     }
+
+    /// Total number of voluntary exits in the pool.
+    pub fn num_voluntary_exits(&self) -> usize {
+        self.voluntary_exits.read().len()
+    }
 }
 
 /// Filter up to a maximum number of operations out of an iterator.