Ensure all versions of pypi METADATA parsing is tested

[AyanSinhaMahapatra]

See all the versions at https://packaging.python.org/en/latest/specifications/core-metadata/#metadata-version, and to support all of these:

• Search github for METADATA files (or look for these in pypi installed wheels) with the specific version of metadata like: Metadata-Version: 2.4 and add examples of these to test
• Compare between the different metadata versions and support newer attributes if any

Follow up on #4174

[Jaishree2310]

@AyanSinhaMahapatra I would like to work on this issue.

[hemantchilkuri]

can you assign me this issue

[pombredanne]

@hemantchilkuri you can see in the history here this PR link:

• Add tests for all PyPI METADATA versions (#4175) #4180
  ... that @alok1304 has opened.
  You are welcomed to help review and refine that PR, but the work is pretty much done there.