refactor: Remove JavaInterface, which causes compilation issues with Bloop

[tgodzik]

I don't think it's used anywhere right now, but we could just move it to a separate module if needed.

[tgodzik]

@alexarchambault do we need that interface anywhere else or is it safe to remove? I can also just move it to another module.

[Gedochao]

LGTM

[alexarchambault]

do we need that interface anywhere else or is it safe to remove? I can also just move it to another module.

Yes, it's used by coursier bootstraps, IIRC. They're written in Java, and can read the proxy config and the default repository list from the Scala CLI config using this API. My bad, they don't rely on this anymore (they must have at some point, possibly only locally on my machine). I guess this can be removed.