Implement import.meta (#2816)
I chose to have the `import.meta.url` to have the relative project path on disk.
Webpack makes it the absolute system path, but that would make the JS output system dependent and I didn't like that. Vite doesn't bundle and uses the browser's behavior, which is the dev server path.
I'm splitting this from the in-progress PR to implement `new URL(…, import.meta.url)` support. That requires a bunch of changes to the analysis code and a new FS content source, so it's taking longer to ship.
Fixes WEB-137.
