* Fix staking `rebond` weight refund


Comment

* use safe arithmetic

* comment

* Add some important events to batch & staking to ensure ease of analysis

* Update frame/staking/src/pallet/mod.rs

Co-authored-by: Zeke Mostov <[email protected]>

* Update lib.rs

* fix test

Co-authored-by: Zeke Mostov <[email protected]>
Co-authored-by: Shawn Tabrizi <[email protected]>

* Reorg migration and pallet and pallet impls

* Fix imports in untouched modules

* Add file headers

* Add header for migrations

* Improve comment

* Move OnOffenceHandler impl for Pallet to impl.rs

* fmt