Multi-Block Election part 0: preparation and some cleanup. (#9442)

* Partially applied

* Everything builds, need to implement compact encoding as well.

* Fix some tests, add a ui test as well.

* Fix everything and everything.

* small nits

* a bunch more rename

* more reorg

* more reorg

* last nit of self-review

* Seemingly fixed the build now

* Fix build

* make it work again

* Update primitives/npos-elections/solution-type/src/lib.rs

Co-authored-by: Guillaume Thiolliere <gui.thiolliere@gmail.com>

* Update primitives/npos-elections/solution-type/src/lib.rs

Co-authored-by: Guillaume Thiolliere <gui.thiolliere@gmail.com>

* nits

* factor out double type

* fix try-build

Co-authored-by: Guillaume Thiolliere <gui.thiolliere@gmail.com>

substrate/bin/node/runtime/src/lib.rs

@@ -548,15 +548,14 @@ parameter_types! {
 
 sp_npos_elections::generate_solution_type!(
 	#[compact]
-	pub struct NposCompactSolution16::<
+	pub struct NposSolution16::<
 		VoterIndex = u32,
 		TargetIndex = u16,
 		Accuracy = sp_runtime::PerU16,
 	>(16)
 );
 
-pub const MAX_NOMINATIONS: u32 =
-	<NposCompactSolution16 as sp_npos_elections::CompactSolution>::LIMIT as u32;
+pub const MAX_NOMINATIONS: u32 = <NposSolution16 as sp_npos_elections::NposSolution>::LIMIT as u32;
 
 /// The numbers configured here should always be more than the the maximum limits of staking pallet
 /// to ensure election snapshot will not run out of memory.
@@ -593,7 +592,7 @@ impl pallet_election_provider_multi_phase::Config for Runtime {
 	type RewardHandler = (); // nothing to do upon rewards
 	type DataProvider = Staking;
 	type OnChainAccuracy = Perbill;
-	type CompactSolution = NposCompactSolution16;
+	type Solution = NposSolution16;
 	type Fallback = Fallback;
 	type WeightInfo = pallet_election_provider_multi_phase::weights::SubstrateWeight<Runtime>;
 	type ForceOrigin = EnsureRootOrHalfCouncil;