masonry: auto-detect default stub packages
This change ensures that stub-only packages are auto-detected when packages is not specified in the project's pyproject.toml. This avoids a common user error when creating a stub-only project managed by poetry.
One draw back of this approach is that we might not be able to support packages that actually want -stubs in their names. Not sure if this is a good practice anyway.
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1.6% Duplication
I am going to close this. It's quite old by now and stub packages are less popular since more and more projects adopt native types.
