Problem: no integration test for acknowledgement of ibc/gravity-bridge token transfer

[yihuang]

test the tokens are refunded if the receiver side failed or timeout for send_to_ethereum/send_to_ibc.

[thomas-nguy]

I think there is no concept of timeout for send_to_ethereum. Means that this operation is irreversible.

It is possible to cancel if the transaction is not included in a batch, but the current way is not ideal because batch are created every x blocks, so it is very hard to be able to cancel on time

[yihuang]

failed ack scenarios are tested both for ibc and gravity-bridge now.