IBC application modules should rename `IsBound` to `HasCapability`

[colin-axner]

Summary

Rename IsBound to HasCapability. IsBound currently checks if the IBC application's scoped keeper has claimed the capability for a portID bounded by the portKeeper. This will make it more clear the difference in functionality between: portKeeper.IsBound and k.IsBound

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[expertdicer]

Can you please review my changes? Thank you