Refactor the balances module (#4649)

* Initially scoping out of the problem

* Remove need for exiry in balance locks.

* Remove expiry from locks.

* Remove supefluous balance test

* Amalgamate pieces of balance module

* Split out vesting

* Fix tests

* Fixes for vesting.

* Docs.

* Weight docs.

* Refactor things in terms of set_balances.

* Switch out ED to be free + reserved.

* Remove on_free_balance_zero and some docs.

* Build fixes

* Update frame/vesting/src/lib.rs

Co-Authored-By: Xiliang Chen <[email protected]>

* Update frame/vesting/src/lib.rs

Co-Authored-By: Xiliang Chen <[email protected]>

* Migration

* Remove superfluous code.

* Test fixes

* Fix some tests

* Fix repatriate reserve

* Fixes

* Add test for migration

* Final cleanups

* Fix

* Indentation.

* Undo unneeded referencing

* Bump runtime version

* Fixes

Co-authored-by: Xiliang Chen <[email protected]>