Convert setup.py to setup.cfg

[mwtoews]

Refer to setuptools' declarative configuration page for moving the static metadata into setup.cfg.

To build:

$ pip install --upgrade build
...
$ python -m build
...
Successfully built memory_profiler-0.59.0.tar.gz and memory_profiler-0.59.0-py3-none-any.whl

both .tar.gz and .whl files should be uploaded to PyPI.

A few other notes:

• Now setup.py is a simple wrapper, which some folks expect to see; it may go away someday
• MANIFEST.in was outdated, and files were included anyways

[fabianp]

looks good to me, thanks!