490b7f322e
I needed this for a test, e.g., to disable a source for an extra build dependency without disabling the source for a workspace member, and had also seen some requests for it. I think it makes sense to allow this. The refactor is fairly mechanical, we go from `SourceStrategy::Enabled|Disabled` to `NoSources::All|None|Package(names)` as we do for other options like `NoBinary`. Related https://github.com/astral-sh/uv/issues/17441