fix: fetch tipsets in a single request

[lemmih]

Summary of changes

Changes introduced in this pull request:

• Tipset messages were being fetched individually and from the general swarm. This PR changes the logic to fetch the messages as a single request directed to the owner of the tipset. This fixes an issue where we couldn't fetch the messages fast enough, and Forest would slowly fall out of sync.

Reference issue to close (if applicable)

Closes #5032

Other information and links

Change checklist

• I have performed a self-review of my own code,
• I have made corresponding changes to the documentation. All new code adheres to the team's documentation standards,
• I have added tests that prove my fix is effective or that my feature works (if possible),
• I have made sure the CHANGELOG is up-to-date. All user-facing changes should be reflected in this document.

[lemmih]

I will do a patch release once this is reviewed and merged.

[LesnyRumcajs]

I'd love if our leading P2P expert could pronounce if we're not missing anything here. @hanabi1224

[hanabi1224]

In the previous logic, bitswap reqeusts are sent to all connected peers, should we fallback to non-source peers if it fails here?

[lemmih]

No, if a peer tells us about a new block without having it themselves, we should ignore it.

[hanabi1224]

Oh wait, as I understand, in gossipsub source could be a proxy peer that does not actually own the block

[hanabi1224]

https://docs.rs/libp2p-gossipsub/latest/libp2p_gossipsub/enum.Event.html#variants

propagation_source: PeerId
The peer that forwarded us this message.

if let gossipsub::Event::Message {
        propagation_source: source,
        message,
        message_id: _,
    } = e
    {
        let topic = message.topic.as_str();
        let message = message.data;
        trace!("Got a Gossip Message from {:?}", source);
        if topic == pubsub_block_str {
            match from_slice_with_fallback::<GossipBlock>(&message) {
                Ok(b) => {
                    emit_event(
                        network_sender_out,
                        NetworkEvent::PubsubMessage {
                            source,
                            message: PubsubMessage::Block(b),
                        },
                    )
                    .await;
                }

[lemmih]

"Fixed" by broadcasting the chain_exchange request. Eventually, all of this code needs to be reworked.