500: Code lens support for running tests r=matklad a=kjeremy
Supports running individual and mod tests.
I feel like this kind of abuses the `Runnables` infrastructure but it works. Maybe later on down the line we should introduce a struct that is really just a tuple of binary, arguments, and environment and pass that back to the client instead. `run_single.ts` is just a paired down version of `runnables.ts` and there is duplication because I think run_single will probably change independent of runnables.
Co-authored-by: Jeremy A. Kolb <jkolb@ara.com>
Co-authored-by: Jeremy Kolb <kjeremy@gmail.com>