This switches to generating per-file targets such as `//executable_semantics/testdata:tuple/equality_false.carbon.test`, instead of one test covering all files. Essentially this relies on bazel instead of lit to handle test parallelization.
There's a small update to update_checks.py to handle the recursive directories. Also, I'm only using one level of nesting in this PR but really no reason we can't do more. I'm just not sure what clustering is best right now.
As a pattern, I'm trying to name all failing tests `fail_*.carbon`.
Jon Meow
Geoff Romer