Add a simple binary that can be used for standalone testing modules

[radu-matei]

Right now, after building a module that contains this library, even if that module is standalone and could be executed with Wasmtime, because of the missing host calls, the test suite in this repo has to be extended before executing the module.

This is time consuming, and it would be helpful to have _something similar to the wasmtime run command that adds this library.