feat: nodes should only perform block proposals services if they know they are the leader

[Maddiaa0]

Overview

ATM, all nodes attempt to create and submit block proposals to each other, regardless if they are the leader or not.

The validator client should sync the current epoch state so a sequencer can know when it is their turn to produce blocks.

related to:
#7962

[LHerskind]

I think some of this will be addressed in #8122, as the sequencer won't make its way into publishing a block if it is not the leader so it don't necessarily deal with it in the validator client?

However, we should alter such that we only attest to proposals by the leader so some validation needed, not sure if this was what you meant.