## Multi Block Election Pallet

This PR adds the first iteration of the multi-block staking pallet. 

From this point onwards, the staking and its election provider pallets
are being customized to work in AssetHub. While usage in solo-chains is
still possible, it is not longer the main focus of this pallet. For a
safer usage, please fork and user an older version of this pallet.

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## Replaces

- [x] https://github.com/paritytech/polkadot-sdk/pull/6034 
- [x] https://github.com/paritytech/polkadot-sdk/pull/5272

## Related PRs: 

- [x] https://github.com/paritytech/polkadot-sdk/pull/7483
- [ ] https://github.com/paritytech/polkadot-sdk/pull/7357
- [ ] https://github.com/paritytech/polkadot-sdk/pull/7424
- [ ] https://github.com/paritytech/polkadot-staking-miner/pull/955

This branch can be periodically merged into
https://github.com/paritytech/polkadot-sdk/pull/7358 ->
https://github.com/paritytech/polkadot-sdk/pull/6996

## TODOs: 

- [x] rebase to mas...