Use proper bounded vector type for nominations (#10601)

* Use proper bounded vector type for nominations

* add docs and tweak chill_other for cleanup purposes

* Fix the build

* remove TODO

* add a bit more doc

* even more docs
gushc

* Update frame/staking/src/pallet/mod.rs

Co-authored-by: Zeke Mostov <z.mostov@gmail.com>

* Update frame/staking/src/pallet/mod.rs

Co-authored-by: Zeke Mostov <z.mostov@gmail.com>

* Fix the nasty bug

* also bound the Snapshot type

* fix doc test

* document bounded_vec

* self-review

* remove unused

* Fix build

* frame-support: repetition overload for bounded_vec

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

* fix

* remove the need to allocate into unbounded voters etc etc

* Don't expect

* unbreal the build again

* handle macro a bit better

Co-authored-by: Zeke Mostov <z.mostov@gmail.com>
Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

substrate/primitives/npos-elections/src/lib.rs

@@ -471,7 +471,7 @@ pub fn is_score_better<P: PerThing>(this: ElectionScore, that: ElectionScore, ep
 /// - It drops duplicate targets within a voter.
 pub fn setup_inputs<AccountId: IdentifierT>(
 	initial_candidates: Vec<AccountId>,
-	initial_voters: Vec<(AccountId, VoteWeight, Vec<AccountId>)>,
+	initial_voters: Vec<(AccountId, VoteWeight, impl IntoIterator<Item = AccountId>)>,
 ) -> (Vec<CandidatePtr<AccountId>>, Vec<Voter<AccountId>>) {
 	// used to cache and access candidates index.
 	let mut c_idx_cache = BTreeMap::<AccountId, usize>::new();
@@ -496,7 +496,7 @@ pub fn setup_inputs<AccountId: IdentifierT>(
 	let voters = initial_voters
 		.into_iter()
 		.filter_map(|(who, voter_stake, votes)| {
-			let mut edges: Vec<Edge<AccountId>> = Vec::with_capacity(votes.len());
+			let mut edges: Vec<Edge<AccountId>> = Vec::new();
 			for v in votes {
 				if edges.iter().any(|e| e.who == v) {
 					// duplicate edge.