Makes explorer/testdata/assoc_const/rewrite_large_type.carbon NOAUTOUPDATE and no-trace because otherwise it takes ~130s to run. With this it's sub-second, explorer is just dumping a lot of trace output (maybe still something to fix).
The intent of this approach is to eliminate recursion limits as a barrier for the parser. While it may not be urgent to address, I want to avoid pouring effort into a parser approach that we don't think will be usable long-term.
Right now this is passing a minor set of tests. It's intended to be enough to show how I'm thinking about flow control for the parser. I'm manually switching back and forth because it seemed like the easiest approach that avoids duplicating tests.
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.
Jon Ross-Perkins
Jon Meow