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-benchmarks/src/fungible/mock.rs

@@ -45,6 +45,8 @@ parameter_types! {
 	pub BlockWeights: frame_system::limits::BlockWeights =
 		frame_system::limits::BlockWeights::simple_max(Weight::from_parts(1024, u64::MAX));
 }
+
+#[derive_impl(frame_system::config_preludes::TestDefaultConfig as frame_system::DefaultConfig)]
 impl frame_system::Config for Test {
 	type BaseCallFilter = Everything;
 	type BlockWeights = ();

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

@@ -51,6 +51,7 @@ parameter_types! {
 		frame_system::limits::BlockWeights::simple_max(Weight::from_parts(1024, u64::MAX));
 }
 
+#[derive_impl(frame_system::config_preludes::TestDefaultConfig as frame_system::DefaultConfig)]
 impl frame_system::Config for Test {
 	type BaseCallFilter = Everything;
 	type BlockWeights = ();