Lazy reaping (#4895)

* Squash and rebase from gav-lazy-reaping

* Bump version

* Bump runtime again

* Docs.

* Remove old functions

* Update frame/balances/src/lib.rs

Co-Authored-By: Shawn Tabrizi <shawntabrizi@gmail.com>

* Update frame/contracts/src/lib.rs

Co-Authored-By: Shawn Tabrizi <shawntabrizi@gmail.com>

* Warnings

* Bump runtime version

* Update frame/democracy/src/lib.rs

Co-Authored-By: Shawn Tabrizi <shawntabrizi@gmail.com>

* Update frame/system/src/lib.rs

* Clean up OnReapAccount

* Use frame_support debug

* Bump spec

* Renames and fix

* Fix

* Fix rename

* Fix

* Increase time for test

Co-authored-by: Shawn Tabrizi <shawntabrizi@gmail.com>
Co-authored-by: Benjamin Kampmann <ben.kampmann@googlemail.com>

substrate/frame/timestamp/src/lib.rs

@@ -278,7 +278,7 @@ mod tests {
 		type ModuleToIndex = ();
 		type AccountData = ();
 		type OnNewAccount = ();
-		type OnReapAccount = ();
+		type OnKilledAccount = ();
 	}
 	parameter_types! {
 		pub const MinimumPeriod: u64 = 5;