Update vc to submit beacon committee selections once per epoch

[nflaig]

We've implemented this based on initial spec which was to submit partial selection proofs each slot but the spec was later changed to just do it once per epoch, see ethereum/beacon-APIs#368

lodestar/packages/validator/src/services/attestation.ts

Line 85 in a8e3089

this.runDistributedAggregationSelectionTasks(fork, duties, slot, signal).catch((e) =>

It makes sense to move the logic from attestation/sync committee service to the corresponding duties services which should also simplify the implementation

Previous PR #5344