Refactor away the entire code of the phragmen election this pallet, and essentially rename it to a generic pallet-generic-elections, that can be used with phragmen or whatever else.

The very important details here is that this pallet uses the order of ElectionResult.winners in the current code, and we need to ensure that in the new ElectionProvider::elect()'s Supports return type, the order is maintained. Perhaps each ElectionProvider would implement a const ORDERED: bool, and then the pallet-elections would ensure that it is always true. All in all, we expect to see this new type in pallet-generic-elections's Config:

type ElectionProvider: ElectionProvider<DataProvider = Self, ORDERED = true>