Outdated details in the `wheel` spec overview (inherited from PEP 425)

@brettcannon migrated the wheel spec from PEP 425 to the relevant spec page in https://github.com/pypa/packaging.python.org/pull/1206/files

Scanning that PR highlighted some original PEP 425 content that hasn't aged well:

• the tag consideration example is Linux based, but doesn't account for the manylinux tags and other Linux-specific tweaks to the tag evaluation process
• the platform tag is still defined as the result of calling distutils.util.get_platform(), but that was just removed from Python 3.12 (and has been deprecated since 3.10). sysconfig.get_platform() is mostly a replacement for that, but as discussed in https://stackoverflow.com/questions/71664875/what-is-the-replacement-for-distutils-util-get-platform it isn't 100% the same, and neither API truly reflects the behaviour of wheel.bdist_wheel.get_platform() (there are some additional pragmatic corrections in https://github.com/pypa/wheel/blob/main/src/wheel/bdist_wheel.py#L47 to deal with some Mac OS X and Linux details)

Those were the two main points I noticed on a quick scan, but PEP 425 is old enough now that there are probably other inconsistencies we missed as the later wheel tagging PEPs adjusted the way things work.

Start with the migrated wheel spec page from packaging.python.org and compare it with PEP 425 and the later wheel-tagging PEPs. Inspect wheel/src/wheel/bdist_wheel.py around the platform corrections noted in the issue. Done means the overview reflects current manylinux and platform-tag behavior and other inconsistencies found during the review.