Move GCV assets to pseudo package

[alancleary]

I've wanted to move the GCV-specific files in the assets/ directory into separate repositories for a while. This is because the functionality is pretty generic and doesn't have a logical place within the GCV code, which is why the files are in the assets/ directory instead of the app/ directory! The files haven't been moved to separate repositories because there's a lot of inter-dependency between them and having them in separate repos would have no benefit to the end-user.

I (finally) realized that these files can be encapsulated in a pseudo-package in the deps/ directory, like the microservice gRPC generation code. This would remove their outdated dependencies from the top-level package.json file and prevent the compiler from giving warnings about the code that aren't relevant to GCV's core functionality. Maybe it will serve as a gateway to moving them to separate repositories...