Remove pkg_resources.build_zipmanifest monkeypatching

[wickman]

This may involve increasing the minimum setuptools version. Another alternative is vendoring setuptools.

[dan-blanchard]

From pypa/setuptools#154, it appears the reason for the monkeypatching was fixed in setuptools 5.4, so setting the minimum version to at least that should do the trick.

[kwlzn]

sgtm. reviewable here: #322

[kwlzn]

btw, it looks like from setuptools 5.4->5.6 you have to set the PKG_RESOURCES_CACHE_ZIP_MANIFESTS environment variable to get this behavior - and it's on by default after 5.7: https://pypi.python.org/pypi/setuptools/5.7#id1

will bump the minimum version in the PR to 5.7 based on this.