Handle the re-org scenario for the proof provider

[nazarhussain]

Problem description

WIth the @lodestar/prover we have the following scenario where we have to update the payloads in case of re-orgs. We need a better way to handle these re-orgs.

lodestar/packages/prover/src/proof_provider/payload_store.ts

Lines 155 to 159 in 08b82af

	// Re-org happened, we need to update the payload
	if (existingELRoot && existingELRoot !== blockELRoot) {
	this.payloads.delete(existingELRoot);
	this.unfinalizedRoots.set(blockCLRoot, blockELRoot);
	}

Solution description

One solution could be that lightclient exposes a re-org event which tells the base slot where re-org happens and then prover should purge and update the payloads from that slot onwards.

Additional context

This issue was extracted from #4706