Stop showing the "Kafka producer log" output view all the time

[fbricon]

I find showing the "Kafka producer log" output view very irritating, every time I click on produce, after I closed the view the 1st time.

[angelozerr]

The output gives the capability to check produce is done. If you don't know that it exists this output, I think you will never show it.

I think we should improve doc in https://github.com/jlandersen/vscode-kafka/blob/master/docs/Producing.md#producing-messages by adding a screenshot after Kafka Producer Log to explain to the user what is the content of Kafka Producer Log

The #117 could fix this check produce is done if we display the produce launch state (Producing, Produced, etc in code lens)