Should physicalLocation disappear?

[ghost]

Copied from sarif-standard/sarif-spec-v1#218, created by @lgolding:

We'd replace location.analysisTarget with location.analysisTargetUri, replace location.resultFile with location.resultFileUri, and introduce property location.region.

The rationale is that you never need a region on both of analysis target and result file.

The initial motivation for considering this change was the introduction of run.analysisTargetUri. We originally considered calling it run.analysisTarget and making it a physicalLocation object whose region would never be used.

@michaelcfanning FYI