Improve and Move Windows Artifact Generation to GitHub Actions

It seems like every release we make some kind of little mistake with the naming or contents of the windows artifacts. See #3012 and #3001 recently.

We should improve our automation here. Moving this workflow to GitHub Actions would allow us to publish the artifacts to the release automatically, removing opportunities for error. This would also advance our broad goal of moving contbuild work off of Appveyor and onto GitHub.

It also came up in [discussion](https://github.com/facebook/zstd/issues/3012#issuecomment-1018100769) that it might be convenient to provide both the full existing .zip as well as a binary-only artifact. So this work item should resolve that.

Moving to GitHub Actions would also allow us to sign those artifacts.