UnreceivedAcks returns all the unreceived IBC acknowledgements associated with a channel and sequences.

Normally the RevisionHeight is incremented at each height while keeping RevisionNumber the same. However some consensus algorithms may choose to reset the height in certain conditions e.g. hard forks, state-machine breaking changes In these cases, the RevisionNumber is incremented so that height continues to be monitonically increasing even as the RevisionHeight gets reset