Add UpdateChannel to Endpoint

[DimitrisJim]

Summary

Would be nice to add a helper function on Endpoint that takes care of setting channel fields as needed. We currently have SetChannelState, would be nice if we could also set the flush status, order, etc without requiring a different function each time. Taking inspiration from Cians suggestion, we could have:

func (endpoint *Endpoint) UpdateChannel(updater func(channel *channeltypes.Channel)) error {
	channel := endpoint.GetChannel()
	updater(&channel)
	endpoint.SetChannel(channel)

	endpoint.Chain.Coordinator.CommitBlock(endpoint.Chain)

	return endpoint.Counterparty.UpdateClient()
}

This could resolve most instances of the pattern: get channel, modify, set channel. Adding this function ideally removes SetChannelState completely and allows SetChannel/GetChannel to be private or, possibly, inlined into UpdateChannel.

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[DimitrisJim]

Would be best to implement and refactor relevant usages after 04-channel-ugprades has been merged.

[colin-axner]

Going to note we should not remove any functions which can be handled with this improvement (SetChannelState for example). We can update our usage internally and add notes in the migration doc but should mark the function as deprecated. There are too many breaking changes in v8 (big release for us + sdk bump + cometbft bump) to justify any code-hygenie breaking changes. We can remove those functions in v9 if we so wish

[DimitrisJim]

ah right, had completely forgotten testing package is actually part of API, that is wild.

[colin-axner]

It's a fairly widely used component of ibc-go. Originally it was designed only for internal usage, but then it fairly quickly was forked a lot to which a second set of improvements (dubbed v2) revitalized the testing pkg to be reuseable outside of ibc-go

[DimitrisJim]

could maybe deprecate these in v10 too along with Coordinator funcs?