Use cosmwasm std mocking in tests

[d3v3us]

We could use mocking IBC functions below to demonstrate IBC working example that comes with some cool example tests.
mock_ibc_channel,
mock_ibc_packet_recv
mock_ibc_channel_connect_ack,
mock_ibc_channel_connect_confirm etc.

[0xekez]

Yes! Would love some help with this if you'd like to contribute. The cw-plus icw20 contract has some nice examples of doing this.