[enhancement] DSLX error messages should have more structured data about related source ranges

[cdleary]

What's hard to do? (limit 100 words)

Right now we just have one span of text that's reported for a given DSLX error message, but you can make much prettier error messages if you can have multiple distinct chunks of text with their own messages/labels.

Current best alternative workaround (limit 100 words)

Right now we just report error messages with respect to one text span and that's fine but could be better.

Your view of the "best case XLS enhancement" (limit 100 words)

We would rely on some facility like Status payloads to help get more metadata about source core ranges related to error messages out to the error printing facilities.