Support generic scroll bar mark sequences (OSC 1337 ; SetMark)

[Tyriar]

Windows Terminal added this recently, there's a bunch of info/research available on microsoft/terminal#11000 and microsoft/terminal#12948

This may be useful in #150833 depending on how clever we want the task integration to be.

https://iterm2.com/documentation-escape-codes.html

[zadjii-msft]

lmao I was largely inspired by you guys 😅 I saw https://code.visualstudio.com/updates/v1_65#_terminal-shell-integration and was like yea now this is a good idea

[Tyriar]

@zadjii-msft hehe. If you go down the full blown shell integration route I can walk you through all the hacks needed to get it working through conpty 😉, It's working quite well now for pwsh but it took a while to get right.

[Tyriar]

If we had a generic mark system we could use them in PartialCommandDetectionCapability so mark decorations show up in the buffer even when shell integration is disabled.

[Tyriar]

This would be a good icon for generic marks:

@misolori should we add an alias for that and/or create a dot codicon?

[miguelsolorio]

@Tyriar that one is specific to the debug icon as it's overlayed and aligned to fit within another icon. we have other dots but also happy to introduce a smaller one if that is desired:

[Tyriar]

@misolori this will be for the naive command detection when shell integration is disabled as well as arbitrary "marks" that either the shell adds or the user does via a command, etc. I figured the little dot would look nice to contrast it strongly with real shell integration (circle-outline and other medium circle icons) and because it's a smaller, more basic version of shell integration.

[miguelsolorio]

Ok, I can add in a request to add a smaller one