The new tags look like '1.21.0.dev0+98.gaa0453721f', where '98' is the
number of commits since the 1.21.0 branch was started and 'aa0453721f'.
The chosen form may be specified in the 'setup.cfg' file. This PR adds
two new files 'numpy/_version.py' and 'numpy/version.py'. The latter
is kept because it is part of the public API and is actually used by
some downstream projects, but it is no longer dynamically created.

See https://github.com/python-versioneer/python-versioneer/ for more
information.

* Create copy of numpy.pxd for Cython 3.0 changes and improve it.

Remove support for Apple Accelerate, since it is buggy. A build error should
occur on most or all setups if linked against Accelerate. Test or import failures
should occur on setups where Accelerate is picked up dynamically.

Co-authored-by: Warren Weckesser <warren.weckesser@gmail.com>

Rationale: it has happened multiple times in the recent past that users
needed to use a more recent Cython than was used to generate the sdist
of the most recent release available on PyPI (e.g. for building with
a not-yet-released version of Python for which a Cython fix just
landed).  The dependency specification and packaging tools have matured
to the point where it should be fine to require Cython to be installed.
Also, we have wheels (and conda-forge packages) for Windows, Linux and
macOS, so this change won't be visible at all to the average user.

Closes gh-13790

Also adds pyproject.toml to MANIFEST.in, it was missing.

remove files that were part of the origal repo
rework randomgen docs to integrate with numpy and fix some links
remove convenience functions, require explicit call to gen.brng
move code out of numpy.random.randomgen into numpy.random