Clean up existing benchmarks (#9839)

* Add FIXME link for a state mod statement

* Remove unused benches feature in ethcore

* Fix evm benches compile

* Fix ethash benches compile

* Switch to criterion

ethcore/src/lib.rs

@@ -15,7 +15,6 @@
 // along with Parity.  If not, see <http://www.gnu.org/licenses/>.
 
 #![warn(missing_docs)]
-#![cfg_attr(feature = "benches", feature(test))]
 
 //! Ethcore library
 //!

ethcore/src/state/mod.rs

@@ -1151,6 +1151,8 @@ impl<B: Backend> State<B> {
 					if require_code {
 						let addr_hash = account.address_hash(a);
 						let accountdb = self.factories.accountdb.readonly(self.db.as_hashdb(), addr_hash);
+
+						// FIXME (Issue #9838): update_account_cache can fail in rare cases, but we cannot return error in RefMut wrapper.
 						Self::update_account_cache(RequireCache::Code, account, &self.db, accountdb.as_hashdb());
 					}
 					account