Create trait for NPoS election algorithms (#9664)

* build the template, hand it over to zeke now.

* Tests working

* save wip

* Some updates

* Some cleanup

* mo cleanin

* Link to issue

* Apply suggestions from code review

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

* Apply suggestions from code review

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

* Apply suggestions from code review

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

* Apply suggestions from code review

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

* Bound accuracy for prepare_election_result

* Use npos_election::Error for phragmms

* save

* Apply suggestions from code review

* Simplify test to use Balancing::set

* Cargo.lock after build

* Revert "Cargo.lock after build"

This reverts commit 7d726c8efa687c09e4f377196b106eb9e9760487.

* Try reduce cargo.lock diff

* Update bin/node/runtime/src/lib.rs

* Comment

* Apply suggestions from code review

* Set balancing directly

* Document som pub items

* Update frame/election-provider-multi-phase/src/unsigned.rs

* Apply suggestions from code review

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

* Improve some comments

* Revert accidental change to random file

* tiney

* revert

Co-authored-by: kianenigma <kian@parity.io>
Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>