Report publish failures for the closed channel as well

[nikita2206]

Proposed Changes

Currently if a channel was closed then when a publish fails to that channel it will not be reported to the metrics, avoiding the usual alert rules set up for the failed publishes counter.

Recently it has been the case for us where publishes started failing following changes in user/permissions setup in our CloudAMQP instance; while looking at how we could alert ourselves if this ever happens again we noticed that our failed publishes metric didn't budge, even though a lot of publishes have in fact failed. (this wasn't the problem because at the time we didn't have an alert set up for this metric anyway but going forward we would love to be able to have it)

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