combine iteratons and tolerance in sp-npos-elections API (#11498)

* Initial implementation of mms

* Some more attempts at `mms`

* Functioning `MMS` algorithm implementation.
Adding some tests too

* More tests and typos fixed.

* Adding fuzzer for `mms`
(but could not test it on Mac M1)

* Missing imports

* Fixing rustdoc

* More accurate implementation of `mms`

* Removing the fuzzer `mms` implementation

* Implementing `NposSolver` for `MMS`
had to add the `Clone` trait, maybe I could see if I can get rid of it.

* Fixing rust docs by adding () to resolve ambiguity

* Amending `unwrap` to `expect`
removing unneeded `Clone` trait

* Removing redundant `mms3.rs`

* Implementing `BalancingConfig` and rustdoc changes

* Implementing `weight` for `MMS`

* Implementing `weight` for `MMS`

* Fixing post merge

* Initial implementation of mms

* Some more attempts at `mms`

* Functioning `MMS` algorithm implementation.
Adding some tests too

* More tests and typos fixed.

* Adding fuzzer for `mms`
(but could not test it on Mac M1)

* Missing imports

* Fixing rustdoc

* More accurate implementation of `mms`

* Removing the fuzzer `mms` implementation

* Implementing `NposSolver` for `MMS`
had to add the `Clone` trait, maybe I could see if I can get rid of it.

* Amending `unwrap` to `expect`
removing unneeded `Clone` trait

* Fixing rust docs by adding () to resolve ambiguity

* Removing redundant `mms3.rs`

* Implementing `BalancingConfig` and rustdoc changes

* Implementing `weight` for `MMS`

* Implementing `weight` for `MMS`

* Fixing post merge

* Removing left over from rebase

* Fixing tests

* Removing unneeded import

* Removing unneeded functions

* Removing useless imports

Co-authored-by: kianenigma <kian@parity.io>