Add CopyUpToDate ETW

[Forgind]

Progress towards #6658

Adds an up-to-date ETW for the Copy task. Also captures metadata copying just because that happens if it was up-to-date. (Should we have a check rather than always copying?)

[rainersigwald]

Is this the right place for these events, to catch the "incremental build copying the same outputs to the same locations" case? I naïvely assumed it would be in DoCopyIfNecessary.

[Forgind]

The part I put ETW traces around looks like "the file at destination was copied from source." DoCopyIfNecessary has "files are the same size and timestamp" and "files have the same name." There's a fourth check buried in DoCopyWithRetries that does a deep file comparison.

Looking at those four, the first sounded sufficient for if it's just an incremental build, and I stopped there because there deeper I try to push it, the more complicated it gets. This is a simple check with no code movement. To add the next level, I'd need three possible ending places, one of which is currently also executed when actually copying, so I would need a little extra control logic there. The last check is in a catch. I think it would be impossible to hit without capturing copies as well without substantial code changes.

I can check to see if my assumption about the first being sufficient is true or just put in the change to capture the first two levels. I don't think it's worth it to try for the third.

[rainersigwald]

I can check to see if my assumption about the first being sufficient is true

Sounds like a plan.

[Forgind]

Specify whether it was up to date or not