Move the substate module into ethcore/executive (#10867)

* substate is not a part of account-state

* fn cleanup_mode is a part of executive.rs

* test_cleanup_mode

ethcore/src/json_tests/executive.rs

@@ -17,7 +17,8 @@
 use std::path::Path;
 use std::sync::Arc;
 use super::test_common::*;
-use account_state::{Backend as StateBackend, State, Substate};
+use account_state::{Backend as StateBackend, State};
+use substate::Substate;
 use executive::*;
 use evm::{VMType, Finalize};
 use vm::{