Pre-compilation of the reporter in build.rs

[mpizenberg]

The elm main for the reporter doesn't need to embed any runtime parameter, it can get all that is needed from flags and ports. This means we could compile it in advance (probably with --optimize and terser too but that has to be checked) and include the compiled JS directly in the executable.

[mpizenberg]

That would also have the advantage of being able to remove the potential reporter dependencies that are not also in the runner dependencies from the default dependencies that are added to the elm.json for the dependency solver.