parse request version in extractor, refactor match_version

[syphar]

So, this is a somewhat mid-sized refactor in how we handle & match version requirements in requests.

The general idea is:

• we are using a new axum extractor to parse the version requirement (web::ReqVersion). It can parse static names like /latest/, but also specific semver::Version and semver::VersionReq. This changes the status code for an invalid version identifier.. Previously we returned a 404, now it will be a 400. I added a custom Path extractor so we have a nice error page on 400 too, so for users it should be fine.
• All places where we use the extracted version identifier we can now use a semver::Version
• match_version and its response types are refactored to use the new ReqVersion.
• in our handlers there was much repetition around how we handle different ReqVersion and redirect in some cases. This is replaced by introducing AxumNope::Redirect and into_canonical_req_version_or_else for the match_version result. This unifies the version identifier canonicalization in more places.
• In there I also added a redirect from newest or semver * to /latest/, which IMO makes more sense.

I think there will also be more edge cases where the exact redirects for version identifiers are not slightly different than before, but IMO this is fine for a (mostly) web interface.

[syphar]

@Nemo157 @GuillaumeGomez any chance for some feedback? I'm aware it's a big PR, but I hope it will improve some readability in the web handlers.

[GuillaumeGomez]

Looks good to me but please wait for @Nemo157 review. :)

[syphar]

@Nemo157 and chance you can find time for at least some design feedback? I would highly appreciate it

[syphar]

@Nemo157 this is ready for another round.

After removing the package_name rename commit and pushing this branch I realized that this might be hard to review because some files with more changes appear as changed again, sorry about that.