IBCModuleV2 Transfer Application Spike

[chatton]

Summary

Spike a transfer IBCModuleV2 implementation.

Leaving a few thoughts about considerations I've had, decisions can be made when finalizing implementation

• should transfer v2 code live in a new module directory, or just under module/transfer/v2
• Do we need a MsgTransfer(V2)? I don't think so if we have MsgSendPacket and all the validation happens there.
• Forwarding logic needs to be refactored, as in V1 we store a full packet, in V2 we are not providing the packet as an application callback argument. I think this can be out of the scope of this spike.
• both ics20-v1 and ics20-v2 should be supported at the application level, same as existing transfer module.
• testing library needs to be updated to account for sending tokens back and forth between chains using V1 and V2 transfer modules.

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