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>

polkadot/xcm/pallet-xcm/src/mock.rs

@@ -16,7 +16,7 @@
 
 use codec::Encode;
 use frame_support::{
-	construct_runtime, match_types, parameter_types,
+	construct_runtime, derive_impl, match_types, parameter_types,
 	traits::{
 		AsEnsureOriginWithArg, ConstU128, ConstU32, Contains, Equals, Everything, EverythingBut,
 		Nothing,
@@ -246,6 +246,7 @@ parameter_types! {
 	pub const BlockHashCount: u64 = 250;
 }
 
+#[derive_impl(frame_system::config_preludes::TestDefaultConfig as frame_system::DefaultConfig)]
 impl frame_system::Config for Test {
 	type RuntimeOrigin = RuntimeOrigin;
 	type RuntimeCall = RuntimeCall;