fix: Remove tests from .whl file (bdist_wheel)

[jfuss]

Issue #, if available:
N/A

Description of changes:
Python wheels, .whl files, produced through python setup.py bdist_wheel do not read or understand MANIFEST.in files. Since we use this file to remove tests modules from the dists, tests end up in the .whl files that get uploaded to PyPi. This PR updates the exclude parameter in find_packages to exclude all test.* modules, following setuptools documentation.

Checklist:

• Write Design Document (Do I need to write a design document?)
• Write unit tests
• Write/update functional tests
• Write/update integration tests
• make pr passes
• Write documentation

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[tbradley-sans]

Hi, I don't totally understand this change, so I'm wondering if it addresses the problem I'm having right now. I just realized that when I do sam build -u somehow some Python unit tests that don't belong to me are getting put into my project's tests directory. They don't have any copyright notices or even code comments (shame, shame) but since they're importing things like serverlessrepo.parser I'm guessing they belong to SAM. True?