Uprade cw20-ics20 to cw 0.15

[orkunkl]

No description provided.

[orkunkl]

There has been changes on IbcAcknowledgement, I stop working on this PR until I get some explanation.

[ethanfrey]

This seems to be updated to 0.15.0 already and uses

        let ack = IbcAcknowledgementWithPacket {
            acknowledgement: IbcAcknowledgement::new(ack_success()),
            original_packet: sent_packet,
        };

to create the acks in tests (which is the new format for 0.15.0).

What is left to do?

[ethanfrey]

This seems to have been done already by @uint

Thanks