Add Output Panel Smart Scroll

[dwilliamson]

Hi @isidorn, this is a replacement PR for #49199 as I broke a few things in my original branch. It contains your suggested changes as everything could be achieved from within outputServices.ts.

Output panel stops scrolling when clicked upon to place the primary cursor. Scrolling resumes when the cursor is placed at the end of the output again.

Fixes #49110.

[isidorn]

@dwilliamson thanks for this PR.
I have tried it out and it works nice. I have pushed a commit on top of this just to have more code reuse a652847

So basically we have changed our default behavior from "always scroll" to "smart scroll" and we still have an option to "scroll lock". This makes sense to me.
The only behavior that I find weird is that if I enable "scroll lock" and I open something else and go back to the output it is locked but the last line is revealed - I would expect my position to be preserved. However this was not introduced by your change as we have that behavior in stable. But if you are interested in fixing that as well a PR would be more than welcome.

fyi @sandy081

[dwilliamson]

Yes, I found that during testing. Because text is cleared between panel switches I couldn't see anywhere the last line position was preserved so just defaulted to going right to the end of the text.

It will probably annoy me enough soon to start solving it.