fix: manage channel addition without show usage

[STDeslandes]

Contributed by STMicroelectronics

What it does

Closes #15081

Make sure the output widget is refreshed even if the channel.show() function is not used if there is only one channel.

How to test

• Create an output channel but don't show it by default ( it should be the only one created ).
• Add some logs in this channel.
• Show the output windows.
• You should see the logs in the output channel you created.

Follow-ups

Breaking changes

• This PR introduces breaking changes and requires careful review. If yes, the breaking changes section in the changelog has been updated.

Attribution

Review checklist

• As an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

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