Migrate pallet-scheduler to pallet attribute macro (#8769)

* migrate to pallet!

* fixes

* fix genesis

* code review fixes

* Update frame/scheduler/src/lib.rs

Co-authored-by: Keith Yeung <kungfukeith11@gmail.com>

* Update frame/scheduler/src/lib.rs

Co-authored-by: Keith Yeung <kungfukeith11@gmail.com>

* Update frame/scheduler/src/lib.rs

Co-authored-by: Keith Yeung <kungfukeith11@gmail.com>

* Update frame/scheduler/src/lib.rs

Co-authored-by: Keith Yeung <kungfukeith11@gmail.com>

* Update frame/scheduler/src/lib.rs

Co-authored-by: Keith Yeung <kungfukeith11@gmail.com>

* fix metadata

Co-authored-by: Keith Yeung <kungfukeith11@gmail.com>

substrate/frame/scheduler/src/benchmarking.rs

@@ -25,7 +25,7 @@ use frame_system::RawOrigin;
 use frame_support::{ensure, traits::OnInitialize};
 use frame_benchmarking::{benchmarks, impl_benchmark_test_suite};
 
-use crate::Module as Scheduler;
+use crate::Pallet as Scheduler;
 use frame_system::Pallet as System;
 
 const BLOCK_NUMBER: u32 = 2;