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/client/evm_test_client.rs

@@ -28,7 +28,8 @@ use trie_vm_factories::Factories;
 use evm::{VMType, FinalizationResult};
 use vm::{self, ActionParams};
 use ethtrie;
-use account_state::{CleanupMode, Substate, State};
+use account_state::{CleanupMode, State};
+use substate::Substate;
 
 use executive_state::ExecutiveState;