Add SetConnectionState in Endpoint

[DimitrisJim]

Summary

Similar to #3947, this is a common operation in many tests, can be:

// SetConnectionState sets a connection state
func (endpoint *Endpoint) SetConnectionState(state connectiontypes.State) error {
	connection := endpoint.GetConnection()

	connection.State = state
	endpoint.SetConnection(connection)

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

	return endpoint.Counterparty.UpdateClient()
}

there's quite a few instances of this in both main and in 04-channel-upgrade.

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[chatton]

See this suggestion a similar concept could be applied to the connection.

[colin-axner]

See this suggestion a similar concept could be applied to the connection.

Yay! I like this suggestion, so SetChannel becomes internal and we replace:

chan := endpointA.GetChannel()
chan.State = types.OPEN
endpointA.SetChannel(chan)

with

endpointA.UpdateChannel(func(channel *channeltypes.Channel) {
    channel.State = types.OPEN
})

and

func (endpoint Endpoint) UpdateChannel(mutate func(channel *channeltypes.Channel)) {
    channel := endpoint.GetChannel()
    
    mutate(channel)
    
    endpoint.setChannel(channel)
}

[colin-axner]

Love to see the testing pkg get some design love :)

[DimitrisJim]

ohhh that's a nice suggestion. Though I doubt there's gonna be many additional fields on the Channel (right?) I do think that's a much cleaner approach.

[DimitrisJim]

note: going to close this issue at some point and open another with Cians suggestion for both Channel/Connection/anything else.

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

[DimitrisJim]

Closing in preference to #3985