PoV-friendly Election Provider Multi Block (iter 1)

[gpestana]

Goals

• implement the EPM-mutiblock pallet and related sub-pallets
• possible to run current non-multiblock staking with this pallet
• local staking environment working as expected with this pallet
• minimal benchmarks

Notable changes/improvements

1. All storage types are bounded and PoV friendly
2. Election happens in a multi-block fashion; Each phase is split into dedicated blockspace per election page
3. Split the EPM pallet into a core pallet and sub crates that handle a specific part of the election (verification, signed, unsigned);
4. Implement a commit-reveal scheme for signed submissions where the staking miners submit the claimed_score and are called to submit the solution corresponding to the submitted score later.
5. Adapt staking miner-v2 to support multipage solutions
6. Ensure unsigned submission supports pagination

Some ideas/sketches:

• https://github.com/paritytech/substrate/tree/kiz-multi-block-election
• https://github.com/paritytech/substrate/tree/kiz-multi-election-pt0-paginated-data-provider

[gpestana]

dev branch at