Consider consolidating project files about pulumi

[ericrudder]

thanks for filing to track. on the argument against, i'm actually more concerned about "other tools" (things we don't write) than our own toolset ... this is (again) an area where i am naive, since i don't know other tool chains. agree we can short-circuit much of this for .9

[joeduffy]

I took a whack at this in #159, but indeed we lose out on some really great tooling that we get for free (e.g., you cannot do Find All References or Refactoring).

I'm punting on this for now. #98 will force our hand to decide to do something here, although that may be as simple as auto-detecting the language's native project file format.

If we want to get to the simpler experience of a single file, we could explore hijacking the language project files, but I still don't want to go there because there's something very clarifying about seeing Lumi.yaml and understanding what is specific to the Lumi system.

At the end of the day, maybe multiple files isn't terrible, as it is very UNIX in the "one thing done well" and separation of concerns departments.