Do not download the entire Deno runtime just to publish a package

[KnorpelSenf]

It would be great to integrate the logic to publish a package directly in the JSR CLI. I don't think it is justified to download a ~140 MB binary and then call into it just so we can upload a few text files to a server.

I understand that this might have been a useful shortcut in the early days because it allowed code re-use from deno publish, but then I'd still like to have this issue to track when this practice ends.