Distutils module are now deprecated and will be removed in Python 3.12.
This replaces it by packaging module and reduces the dependency to it.

refs: #9820

`SphinxDirective.get_source_info()` returns the pair of fullpath of
source and current line number.  But our logging module expects one of
these:

* A string consists of fullpath and current line number
* A pair of docname and current line number

To show correct location for warnings, this adds `get_location()` method
that returns the former one.

Note: This also modifies C/C++ domains.

.. note::

   $ find sphinx tests LICENSE doc/conf.py -type f -exec sed -i '' -e 's/2007\-20../2007-2021/' {} \;
   $ git co sphinx/locale/**/*.js sphinx/templates/epub3/mimetype

Keep imports alphabetically sorted and their order homogeneous across
Python source files.

The isort project has more feature and is more active than the
flake8-import-order plugin.

Most issues caught were simply import ordering from the same module.
Where imports were purposefully placed out of order, tag with
isort:skip.