rust-cpython: switch logging facade from `simple_logger` to `env_logger`
`simple_logger` is just too simple. `env_logger` supports logging to `stderr`,
and logging filtering, for example, which are becoming necessary now. The
project is nicely active.
Differential Revision: https://phab.mercurial-scm.org/D8990
% creating repo
% add and commit
C test.py
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M test.py