Validators circuit: shuffling check

Design and prototype a shuffling chip for constraining order of validators based on [swap-or-not](https://eth2book.info/capella/part2/building_blocks/shuffling/#swap-or-not-specification) shuffling algorithm and RANDAO-generated randomness as a part of [`BeaconState.randao_mixes`](https://eth2book.info/capella/annotated-spec/#beaconstate). The goal is to empirically estimate the cost of including this check in the final system. This is the opposite of #12.

> **Note**: Since it's pretty clear that this would be expensive and it's very desirable not to include this check, this circuit should be done in the simplest and quickest way possible.

Regardless of the experimental findings, the design should be included in the spec.

### [Spec](https://hackmd.io/@timofey/ByTGrG9S2#State-tree)

### References
- an optimized "fast" version of shuffling https://github.com/protolambda/eth2-shuffle/blob/master/shuffle.go