Python - do not install eggs

As a part of our current testing infrastructure, some packages can get installed under .eggs/. This install is racey (unlike installing via pip), and recently has become very racey with the addition of setup_requires (for pytest) and tests_require (for interactive runner).

Removing the setup_requires and tests_require sections from setup.py should mitigate flakiness.

See this discussion as well:
https://lists.apache.org/thread.html/6d8b54bbb80eaf58bb3daf1887134e2f6c1a01ca349ce26c8e561085@%3Cdev.beam.apache.org%3E

chadrik