This reworks the new `Pypi` JSON API implementation to use
`Json::find_versions` in `Pypi::find_versions`, borrowing some of the
approach from the `Crate` strategy.
Besides that, this pares down the fields in the
`::generate_input_values` return hash to only `:url`, as we're not
using a generated regex to match version information in this setup.
This adds a `provided_content` parameter to `::find_versions` as part
of this process and I will expand the `Pypi` tests to increase
coverage (like the `Crates` tests) in a later PR. 75% of `Pypi` checks
are failing at the moment (with some returning inaccurate version
information), so the current priority is getting this fix merged in
the short-term.
935eb89eca