Ranked Collective pallet (#11548)

* Ranked Collective pallet

* Fixes

* benchmarks

* Weights

* Allow class voting in rank
Use bare ayes for calculating support.
Allow only promotion/demotion by one rank only.
Allow removal of member with rank zero only.
Use new Tally API

* Index by rank, still O(1).

* Custom vote weights

* Formatting

* Update frame/ranked-collective/src/lib.rs

* Broken :(

* origin guard; cleanup uses new API

* Formatting

* Promote/demote by rank

* Formatting

* Use new API

* Remove code in another PR

* Remove code in another PR

* Formatting

* Remove code in another PR

* Docs

* Docs

* Bump

* Fixes

* Formatting

* Fixes

substrate/frame/support/src/storage/mod.rs

@@ -27,7 +27,7 @@ use crate::{
 use codec::{Decode, Encode, EncodeLike, FullCodec, FullEncode};
 use sp_core::storage::ChildInfo;
 use sp_runtime::generic::{Digest, DigestItem};
-use sp_std::prelude::*;
+use sp_std::{marker::PhantomData, prelude::*};
 
 pub use self::{
 	transactional::{
@@ -51,6 +51,10 @@ pub mod types;
 pub mod unhashed;
 pub mod weak_bounded_vec;
 
+/// Utility type for converting a storage map into a `Get<u32>` impl which returns the maximum
+/// key size.
+pub struct KeyLenOf<M>(PhantomData<M>);
+
 /// A trait for working with macro-generated storage values under the substrate storage API.
 ///
 /// Details on implementation can be found at [`generator::StorageValue`].