Untie the lifetime of returns and the lifetime of module in pybindings

Summary: In cpp these are tied to not force a clone on everyone due to performance overhead and there are ways around it with customizing your own output buffer. In python which is just for testing really its fine to always clone and avoid unintuitive behavior

Reviewed By: dulinriley

Differential Revision: D47933661

fbshipit-source-id: 84178bfd5e9e055078b2d7cfd2c6739df2b3e1ea