Add optional languageId to window.createOutputChannel API (#19561)

[gjsjohnmurray]

This PR fixes #19561 by implementing proposed API which adds an optional languageId param to window.createOutputChannel.

This was previously suggested by @ArtemGovorov and was supported at the time by @jrieken.

It was later raised as a solution for #19561, opened by @formulahendry.

[gjsjohnmurray]

@sandy081 any chance you could consider merging this in time for Monday's endgame?

[sandy081]

I am sorry that I have to postpone this for the next milestone as this has to be discussed in our API sync meeting first. The last API sync for this milestone finished today and unfortunately I missed checking this in time. Since there is no urgency, I will plan this for next milestone and discuss in our API sync.

[gjsjohnmurray]

@sandy081 no worries. I know you have been busy with other things.

[gjsjohnmurray]

@sandy081 now that 1.64 has shipped, when will the next API sync meeting happen? I'd like to get this into Insiders soon.

[sandy081]

@gjsjohnmurray Thanks for reminding. API call is today. As per the process we will first add it to the proposed API and after getting some feedback we will finalize it. So most probably this will be a proposed API in this month and goes into finalization next month.

[sandy081]

Changes look good. Did some small clean ups. Approved.