tests are missing from pypi sdist

[dvzrv]

Hi! I'm packaging python-vmprof for Arch Linux. We usually use pypi as upstream (it has a more unique naming strategy when it comes to source tarballs).
However, when building 0.4.15 I noticed, that vmprof/test is missing from the sdist.

As during packaging usually all tests are run to ensure the compatibility with the system-wide provided versions of other python libraries and python itself, it would be really great to add the files to the sdist! Thank you!

[mattip]

I just released 0.4.17 and I see the tests are still not in the source tarball. I see there is some discussion about this in a python discourse thread and I would agree with the sentiment that we should include them in the wheels and tarballs, they are not very large.

I am not sure what needs to change in the setup.py to include the tests.

We should also move away from setup.py to use pyproject.toml + a build backend like meson.