* Collection of enhancement for staking phragmen.

* Ditch signed extension

* Fix build

* Update frame/staking/src/lib.rs

Co-Authored-By: thiolliere <gui.thiolliere@gmail.com>

* Update frame/staking/src/tests.rs

Co-Authored-By: thiolliere <gui.thiolliere@gmail.com>

* Fix reward limits

* Disallow payout_stakers

* Remove unused import

Co-authored-by: thiolliere <gui.thiolliere@gmail.com>