Moves all test runtimes to use derive_impl (#2409)

Step in https://github.com/paritytech/polkadot-sdk/issues/171

This PR adds `derive_impl` on all `frame_system` config impls for mock
runtimes. The overridden configs are maintained as of now to ensure
minimal changes.

---------

Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

substrate/bin/node-template/pallets/template/src/mock.rs

@@ -1,5 +1,8 @@
 use crate as pallet_template;
-use frame_support::traits::{ConstU16, ConstU64};
+use frame_support::{
+	derive_impl,
+	traits::{ConstU16, ConstU64},
+};
 use sp_core::H256;
 use sp_runtime::{
 	traits::{BlakeTwo256, IdentityLookup},
@@ -17,6 +20,7 @@ frame_support::construct_runtime!(
 	}
 );
 
+#[derive_impl(frame_system::config_preludes::TestDefaultConfig as frame_system::DefaultConfig)]
 impl frame_system::Config for Test {
 	type BaseCallFilter = frame_support::traits::Everything;
 	type BlockWeights = ();