Final changes for fusaka-devnet-2 (#7655)

Closes #7467.

This PR primarily addresses [the P2P changes](https://github.com/ethereum/EIPs/pull/9840) in [fusaka-devnet-2](https://fusaka-devnet-2.ethpandaops.io/). Specifically:

* [the new `nfd` parameter added to the `ENR`](https://github.com/ethereum/EIPs/pull/9840)
* [the modified `compute_fork_digest()` changes for every BPO fork](https://github.com/ethereum/EIPs/pull/9840)

90% of this PR was absolutely hacked together as fast as possible during the Berlinterop as fast as I could while running between Glamsterdam debates. Luckily, it seems to work. But I was unable to be as careful in avoiding bugs as I usually am. I've cleaned up the things *I remember* wanting to come back and have a closer look at. But still working on this.

Progress:
* [x] get it working on `fusaka-devnet-2`
* [ ] [*optional* disconnect from peers with incorrect `nfd` at the fork boundary](https://github.com/ethereum/consensus-specs/pull/4407) - Can be addressed in a future PR if necessary
* [x] first pass clean-up
* [x] fix up all the broken tests
* [x] final self-review
* [x] more thorough review from people more familiar with affected code

beacon_node/lighthouse_network/src/service/mod.rs

@@ -193,10 +193,15 @@ impl<E: EthSpec> Network<E> {
 
         // set up a collection of variables accessible outside of the network crate
         // Create an ENR or load from disk if appropriate
+        let next_fork_digest = ctx
+            .fork_context
+            .next_fork_digest()
+            .unwrap_or_else(|| ctx.fork_context.current_fork_digest());
         let enr = crate::discovery::enr::build_or_load_enr::<E>(
             local_keypair.clone(),
             &config,
             &ctx.enr_fork_id,
+            next_fork_digest,
             &ctx.chain_spec,
         )?;
 
@@ -280,27 +285,26 @@ impl<E: EthSpec> Network<E> {
             // Set up a scoring update interval
             let update_gossipsub_scores = tokio::time::interval(params.decay_interval);
 
-            let current_and_future_forks = ForkName::list_all().into_iter().filter_map(|fork| {
-                if fork >= ctx.fork_context.current_fork() {
-                    ctx.fork_context
-                        .to_context_bytes(fork)
-                        .map(|fork_digest| (fork, fork_digest))
-                } else {
-                    None
-                }
-            });
+            let current_digest_epoch = ctx.fork_context.current_fork_epoch();
+            let current_and_future_digests =
+                ctx.chain_spec
+                    .all_digest_epochs()
+                    .filter_map(|digest_epoch| {
+                        if digest_epoch >= current_digest_epoch {
+                            Some((digest_epoch, ctx.fork_context.context_bytes(digest_epoch)))
+                        } else {
+                            None
+                        }
+                    });
 
-            let all_topics_for_forks = current_and_future_forks
-                .map(|(fork, fork_digest)| {
+            let all_topics_for_digests = current_and_future_digests
+                .map(|(epoch, digest)| {
+                    let fork = ctx.chain_spec.fork_name_at_epoch(epoch);
                     all_topics_at_fork::<E>(fork, &ctx.chain_spec)
                         .into_iter()
                         .map(|topic| {
-                            Topic::new(GossipTopic::new(
-                                topic,
-                                GossipEncoding::default(),
-                                fork_digest,
-                            ))
-                            .into()
+                            Topic::new(GossipTopic::new(topic, GossipEncoding::default(), digest))
+                                .into()
                         })
                         .collect::<Vec<TopicHash>>()
                 })
@@ -308,7 +312,7 @@ impl<E: EthSpec> Network<E> {
 
             // For simplicity find the fork with the most individual topics and assume all forks
             // have the same topic count
-            let max_topics_at_any_fork = all_topics_for_forks
+            let max_topics_at_any_fork = all_topics_for_digests
                 .iter()
                 .map(|topics| topics.len())
                 .max()
@@ -359,7 +363,7 @@ impl<E: EthSpec> Network<E> {
             // If we are using metrics, then register which topics we want to make sure to keep
             // track of
             if ctx.libp2p_registry.is_some() {
-                for topics in all_topics_for_forks {
+                for topics in all_topics_for_digests {
                     gossipsub.register_topics_for_metrics(topics);
                 }
             }
@@ -1347,6 +1351,12 @@ impl<E: EthSpec> Network<E> {
         self.enr_fork_id = enr_fork_id;
     }
 
+    pub fn update_nfd(&mut self, nfd: [u8; 4]) {
+        if let Err(e) = self.discovery_mut().update_enr_nfd(nfd) {
+            crit!(error = e, "Could not update nfd in ENR");
+        }
+    }
+
     /* Private internal functions */
 
     /// Updates the current meta data of the node to match the local ENR.