Remove support for crossing hellos for connection and channel handshake

[ancazamfir]

Summary of Bug

Crossing hellos have been deprecated since ibc-go v4.0.0. We should cleanup the code and tests.

Version

Steps to Reproduce

Acceptance Criteria

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[seanchen1991]

@ancazamfir could you provide some more details on this? Not really sure how to go about this.