feat: add compute shuffled index

[wemeetagain]

Motivation

• Electra: performance issue computing sync committee indices lodestar#7366

Description

• mostly a transliteration of fix: improve sync committee updates lodestar#7456
• TODO
  • add getNextSyncCommittee
  • tests

current benchmark

  computeIndices
    ✔ JS   - computeSyncCommitteeIndices - 16384 indices                  2.647731 ops/s    377.6818 ms/op        -         10 runs   4.52 s
    ✔ RS   - computeSyncCommitteeIndices - 16384 indices                  211.2437 ops/s    4.733870 ms/op        -         45 runs  0.716 s
    ✔ JS   - computeSyncCommitteeIndices - 250000 indices                 2.745048 ops/s    364.2924 ms/op        -         10 runs   4.45 s
    ✔ RS   - computeSyncCommitteeIndices - 250000 indices                 124.8175 ops/s    8.011699 ms/op        -         27 runs  0.725 s
    ✔ JS   - computeSyncCommitteeIndices - 1000000 indices                2.689285 ops/s    371.8460 ms/op        -         10 runs   4.48 s
    ✔ RS   - computeSyncCommitteeIndices - 1000000 indices                94.51259 ops/s    10.58060 ms/op        -         21 runs  0.731 s