feat(pallet-ranked-collective): added types

[PraetorP]

This PR added associated types(AddOrigin & RemoveOrigin) to Config.It allows you to decouple types and areas of responsibility, since at the moment the same types are responsible for adding and promoting(removing and demoting).

/// The origin required to add a member.
type AddOrigin: EnsureOrigin<Self::RuntimeOrigin, Success = ()>;

/// The origin required to remove a member. The success value indicates the
/// maximum rank *from which* the removal may be.
type RemoveOrigin: EnsureOrigin<Self::RuntimeOrigin, Success = Rank>;

To achieve the backward compatibility, the users of the pallet can use the old type via the new morph:

type AddOrigin = MapSuccess<PromoteOriginType, ReplaceWithDefaultFor<()>>;

Polkadot companion: PraetorP/polkadot#2