Fix the broken weight multiplier update function (#6334)

* Initial draft, has some todos left

* remove ununsed import

* Apply suggestions from code review

* Some refactors with migration

* Fix more test and cleanup

* Fix for companion

* Apply suggestions from code review

Co-authored-by: Alexander Popiak <[email protected]>

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

* Fix weight

* Add integrity test

* length is not affected.

Co-authored-by: Alexander Popiak <[email protected]>