Fix ConsumersOpened counter not incremented when use multitopic or regexp consumer

[PowerStateFailure]

Motivation

There was a kind of weird behavior when internal consumers created by multitopic- or regexp consumer are not counted as opened, but do as closed, so we can see in Prometheus that there were more consumers closed than opened.

Modifications

Drop topicSubscribe function, increment ConsumersOpened counter on each success newInternalConsumer call similary to what's already done in reader and producer constructors.

Verifying this change

• Make sure that the change passes the CI checks.

This change is a trivial rework / code cleanup without any test coverage.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): (yes / no)
• The public API: (yes / no)
• The schema: (yes / no / don't know)
• The default values of configurations: (yes / no)
• The wire protocol: (yes / no)

Documentation

• Does this pull request introduce a new feature? (yes / no)
• If yes, how is the feature documented? (not applicable / docs / GoDocs / not documented)
• If a feature is not applicable for documentation, explain why?
• If a feature is not documented yet in this PR, please create a followup issue for adding the documentation

[cckellogg]

LGTM any idea why CI is failing?

[wolfstudy]

ping @PowerStateFailure please merge master code and fix Action CI

[wolfstudy]

LGTM +1

[wolfstudy]

ping @PowerStateFailure please merge master code and fix the action CI, thanks.