Replace hyperx with minimal, vendored Content-Range parsing

[huonw]

This removes the hyperx (https://github.com/dekellum/hyperx) dependency, because that dependencies takes the unusual approach of putting strict upper bounds on dependencies (not just restricting to semver-compatible versions, as Cargo does by default), and seems to be relatively unmaintained: a fix dekellum/hyperx#40 for that issue hasn't been merged for a while.

This dependency is only used to parse the Content-Range header value. This header is very simple, and thus it's easy to implement what's required directly in gha-toolkit.

Similar to #6, removing this dependency makes integrating gha-toolkit into other projects much easier. For example, in pantsbuild/pants#17840, I had use Cargo's [patch.crates-io] directive to refer to dekellum/hyperx#40, or else cargo couldn't find a valid set of dependencies (that is, I literally couldn't add gha-toolkit as a dependency due to hyperx).

This also positively improves the transitive dependencies of gha-toolkit too:

• language-tags and matches are no longer required (i.e. the dependency tree/compile times is smaller)
• bytes, form_urlencoded, idna, percent-encoding, url can use newer versions, since hyperx's upper bounds have disappeared