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>