Investigate whether github chores can be used to show AVA failures inline

[spectranaut]

See some discussion here: #1501 (comment)

Because the failures might come from unchanged files (in fact, they more frequently do), we would have to use the "Unchanged files with check annotations" beta feature.

[nschonni]

Also related #1515 and #1517
The only part I'm not sure for the problem matcher is getting the line/column number from the Ava results.
Slightly different in Actions, but https://code.visualstudio.com/Docs/editor/tasks#_defining-a-problem-matcher covers the recursive matching if it's needed