This referendum enables two approval voting protocol improvements that are a prerequisite to **scale up the number of parachain validators to 500**. 

Once enacted, the validators will start using the new format for approval voting assignments and also approve multiple candidates under a single singature. The impact is the reduction of network bandwidth and CPU usage of the approval voting protocol.

High level tracking issue for scaling the validator set: https://github.com/paritytech/roadmap/issues/26

Relevant node side changes (released Q4 2023): 
- v2 assignment certificates : https://github.com/paritytech/polkadot-sdk/pull/1178
- approval of multiple candidates with single signature: https://github.com/paritytech/polkadot-sdk/pull/1191



See [`Pallet::dispatch_whitelisted_call_with_preimage`].

- **Problem Statement:** Enhancing approval voting protocols to accommodate 500 parachain validators.
- **Significance:** Reducing network bandwidth and CPU usage.
- **Proposed Solution:** Implementing new approval voting format and allowing approval of multiple candidates with a single signature.
- **Expected Outcomes:** Improved scalability and efficiency for validators.

#392 Enable approval voting protocol improvements