Moving NposSolution to frame (#11031)

* Move `sp-npos-elections-solution-type`
to `frame-election-provider-support`
First stab at it, will need to amend some more stuff

* Fixing tests

* Fixing tests

* Fixing cargo.toml for std configuration

* fmt

* Committing suggested changes
renaming, and re exporting macro.

* Removing unneeded imports

* Move `NposSolution` to frame

* Removing `npos_election` dependencies
Implementing _fpes better

* some feedback for moving NPoSSolution to frame

* fmt

* more formatting

* Fixed some imports and fmt

* Fixing docs

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

substrate/frame/election-provider-multi-phase/src/benchmarking.rs

@@ -28,7 +28,6 @@ use frame_support::{
 use frame_system::RawOrigin;
 use rand::{prelude::SliceRandom, rngs::SmallRng, SeedableRng};
 use sp_arithmetic::{per_things::Percent, traits::One};
-use sp_npos_elections::IndexAssignment;
 use sp_runtime::InnerOf;
 
 const SEED: u32 = 999;
@@ -461,6 +460,7 @@ frame_benchmarking::benchmarks! {
 			T::BenchmarkingConfig::DESIRED_TARGETS[1];
 		// Subtract this percentage from the actual encoded size
 		let f in 0 .. 95;
+		use frame_election_provider_support::IndexAssignment;
 
 		// Compute a random solution, then work backwards to get the lists of voters, targets, and
 		// assignments