Consider deleting BuildEventArgs.ThreadId

[KirillOsenkov]

BuildEventArgs.ThreadId appears to be unused:
https://source.dot.net/#Microsoft.Build.Framework/BuildEventArgs.cs,e7fedb352ddef2cb,references

Consider deleting it to save memory and perf.

[ladipro]

Team Triage: @KirillOsenkov it looks like the property is read by many FormatEventMessage overloads. Are you saying that there is opportunity to refactor the code further to make it redundant? If so, can you please elaborate?

[KirillOsenkov]

I guess my question is even if it’s currently used, how useful is it? What is it for?

[KirillOsenkov]

@rainersigwald do you think I can kill ThreadId?

[rainersigwald]

I can't think of a reason why it would ever be very useful. However, since it's an ancient public field I'm a bit worried about impact to third-party folks who saw it and access it even if it's not useful.

I'd be willing to deprecate + always return 0 or something for 17.0, I think, but am hesitant to outright remove.

[KirillOsenkov]

Yup, sounds good