feat: modify `aggsender-proposer` function to poll validators to know if he needs to sign the certificate locally

[goran-ethernal]

Modify pollValidatorCommittee function on aggsender-proposer to know about the proposer key to locally sign the proposal.

We should also sort the signatures by the validator indexes, after we get them.

Also required to refactor function pollValidatorCommitteebecause is too long