decl_module! macro: use 'frame_system' instead of system as default ident (#6500)

* Use frame_system as default ident.

* Remove unused 'frame_system' to 'system' renaming.

* Fix construct_runtime_ui tests.

* Rename system to frame_system in sudo/utility pallet test.

* Bump runtime impl_version.

* Update formatting.

Author: valeriikharkin

src/lib.rs

@@ -33,7 +33,7 @@ use serde::{Serialize, Deserialize};
 use frame_support::{ensure, decl_module, decl_storage, decl_event, decl_error};
 use frame_support::weights::Weight;
 use frame_support::traits::{Currency, WithdrawReason, ExistenceRequirement, Get};
-use frame_system::{self as system, ensure_signed};
+use frame_system::ensure_signed;
 use sp_runtime::ModuleId;
 use sp_core::{U256, H256, H160, Hasher};
 use sp_runtime::{