Add Authorize Upgrade Pattern to Frame System (#2682)

Adds the `authorize_upgrade` -> `enact_authorized_upgrade` pattern to
`frame-system`. This will be useful for upgrading bridged chains that
are under the governance of Polkadot without passing entire runtime Wasm
blobs over a bridge.

Notes:

- Changed `enact_authorized_upgrade` to `apply_authorized_upgrade`.
Personal opinion, "apply" more accurately expresses what it's doing. Can
change back if outvoted.
- Remove `check_version` in favor of two extrinsics, so as to make
_checked_ the default.
- Left calls in `parachain-system` and marked as deprecated to prevent
breaking the API. They just call into the `frame-system` functions.
- Updated `frame-system` benchmarks to v2 syntax.

---------

Co-authored-by: command-bot <>

cumulus/pallets/parachain-system/src/tests.rs

@@ -1127,8 +1127,9 @@ fn upgrade_version_checks_should_work() {
 			let new_code = vec![1, 2, 3, 4];
 			let new_code_hash = H256(sp_core::blake2_256(&new_code));
 
-			let _authorize =
-				ParachainSystem::authorize_upgrade(RawOrigin::Root.into(), new_code_hash, true);
+			#[allow(deprecated)]
+			let _authorize = ParachainSystem::authorize_upgrade(RawOrigin::Root.into(), new_code_hash, true);
+			#[allow(deprecated)]
 			let res = ParachainSystem::enact_authorized_upgrade(RawOrigin::None.into(), new_code);
 
 			assert_eq!(expected.map_err(DispatchErrorWithPostInfo::from), res);