wheel: Fails to build wheel for Python 3.10

Encountered while looking into pypa/pip#8312.

$ python --version  # Built from master.
Python 3.10.0a0
$ python -c 'import setuptools; print(setuptools.__version__)'
46.0.0
$ python -m pip install --no-build-isolation -U "wheel @ git+https://github.com/pypa/wheel.git"
...
Successfully installed wheel-0.34.2
$ git clone https://github.com/cython/cython.git
$ cd cython
$ python setup.py bdist_wheel
...
running install_scripts
Traceback (most recent call last):
  File "cython/setup.py", line 291, in <module>
    run_build()
  File "cython/setup.py", line 228, in run_build
    setup(
  File "pip-8312/lib/python3.10/site-packages/setuptools/__init__.py", line 144, in setup
    return distutils.core.setup(**attrs)
  File "python3.10/lib/python3.10/distutils/core.py", line 148, in setup
    dist.run_commands()
  File "python3.10/lib/python3.10/distutils/dist.py", line 966, in run_commands
    self.run_command(cmd)
  File "python3.10/lib/python3.10/distutils/dist.py", line 985, in run_command
    cmd_obj.run()
  File "pip-8312/lib/python3.10/site-packages/wheel/bdist_wheel.py", line 328, in run
    impl_tag, abi_tag, plat_tag = self.get_tag()
  File "/lib/python3.10/site-packages/wheel/bdist_wheel.py", line 278, in get_tag
    assert tag in supported_tags, "would build wheel with unsupported tag {}".format(tag)
AssertionError: would build wheel with unsupported tag ('cp310', 'cp310', 'linux_x86_64')

It seems like bdist_wheel is using different tag schemes to build and check the tags. The assertion uses packaging.tags, which correctly tag Python 3.10 as cp3_10 (see pypa/packaging#240), but the build part incorrectly tries to use cp310, causing the assertion error.

Side note: The sdist has a packaging issue. --no-build-isolation is needed since otherwise the build fails with ModuleNotFoundError: No module named 'packaging'.