python3: Split setuptools into separate source package

python3: Split setuptools into separate source package

Packaging setuptools from a separate source package allows it to stay
updated with upstream.

Host setuptools will remain installed as part of python3. Host
setuptools is used in a much more controlled way and so is less critical
for it to track upstream.

setuptools was in a separate source package that was removed in
a53d0c5a403d1669e2cf6c59c2be6a9d3ed633a0; this work is not based on that
earlier package.

Signed-off-by: Jeffery To <jeffery.to@gmail.com>