RegisterPayee defines a rpc handler method for MsgRegisterPayee RegisterPayee is called by the relayer on each channelEnd and allows them to set an optional payee to which reverse and timeout relayer packet fees will be paid out. The payee should be registered on the source chain from which packets originate as this is where fee distribution takes place. This function may be called more than once by a relayer, in which case, the latest payee is always used.