Add multihop support to packet relaying

[joaotav]

Part of: #3940

Summary

• Add support for multihop SendPacket events on collect_events()
• Add a function build_hops_from_connection_ids() to reconstruct ConnectionHops based on a ChainId and Vec<ConnectionId>
• Add multihop support to counterparty_chain_from_channel()
  • Add multihop support to channel_connection_client()
    • Change ChannelConnectionClient struct into an enum with variants for single-hop and multihop channels.
• Add multihop channel support to RelayPath

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