Reject wheels with multiple .dist-info directories (#19986)
Multiple dist-info directories are confusing and can lead to correctness
problems, as they pretend another package is present. They are not
allowed in wheels, and we shouldn't support them.
pip blocks multi dist-info directories, meaning this shouldn't cause
significant breakage:
https://github.com/pypa/pip/blob/72e6c5942802410b6e1cf4ed1953162b5fbea2ba/src/pip/_internal/utils/wheel.py#L52
