Poll block proposer duties before an epoch starts

[twoeths]

Problem description

Right now Lodestar has a risk of missing block proposal at start slot of epoch since it has to poll for proposer duties (and due to I/O lag it may take up to 2s for it which make the block proposal very late into the slot)

Solution description

We already have PrepareNextSlotScheduler run at 2/3 of slot, if we can make sure it runs in less than 2s consistently we can poll for block proposer duties for next epoch 2s before the slot

One blocker for this is #5409

Additional context

No response

[twoeths]

state transition runs in <3s a lot of time so I think we can poll next epoch's proposer duties 1s in advance

once we improve epoch transition time to be consistently <2s, we can run this 2s before next epoch

[twoeths]

To add more context, normally getProposerDuties is very fast but due to I/O lag issue sometimes it's up to 2s, that's why I'd like to improve epoch transition and poll proposer duties 2s before next epoch

Jul-23 12:06:47.012[]                ^[[34mdebug^[[39m: HttpClient request routeId=getProposerDuties
Jul-23 12:06:49.165[]                ^[[34mdebug^[[39m: HttpClient response routeId=getProposerDuties