IBC v2 spec issues

## Context I'm re-reviewing the IBC v2 specs because there have been a few changes since I last read it. ## Problems 1. The Packet type appears incorrect. It contains channel and port IDs which do not match the implementation in ibc-go v10.0.0-rc3 https://github.com/cosmos/ibc/blob/7a5a7482482e41be98b3759233b9756e373d732d/spec/eureka/README.md?plain=1#L141-L151 https://github.com/cosmos/ibc-go/blob/e9522265bf0b4f5fd514ed25c519cfa2970138de/modules/core/04-channel/v2/types/packet.pb.go#L62-L76 2. There is no mapping of channelIdentifiers in https://github.com/cosmos/ibc/blob/7a5a7482482e41be98b3759233b9756e373d732d/spec/eureka/README.md?plain=1#L161-L170