eip7732: add gossip rule for old payloads (#4695)

This additional gossip rule is needed on the `ExecutionPayloadEnvelope`
per [today's breakout room
call](ethereum/pm#1759)

Author: ethDreamer

specs/gloas/p2p-interface.md

@@ -228,6 +228,9 @@ The following validations MUST pass before forwarding the
   the block is retrieved).
 - _[IGNORE]_ The node has not seen another valid
   `SignedExecutionPayloadEnvelope` for this block root from this builder.
+- _[IGNORE]_ The envelope is from a slot greater than or equal to the latest
+  finalized slot -- i.e. validate that
+  `envelope.slot >= compute_start_slot_at_epoch(store.finalized_checkpoint.epoch)`
 
 Let `block` be the block with `envelope.beacon_block_root`. Let `bid` alias
 `block.body.signed_execution_payload_bid.message` (notice that this can be