Implement PEP-592 - Adding “Yank” Support

[jobselko]

PEP-592

This PEP proposes adding the ability to mark a particular file download on a simple repository as “yanked”. Yanking a file allows authors to effectively delete a file, without breaking things for people who have pinned to exactly a specific version.
It also changes to the canonical source for the simple repository API to the Simple Repository API reference document.

[jobselko]

The implementation should be similar to pulp/pulp_rust#14