Regression in rendering of dependency version requirements

[dtolnay]

Before	After
(screenshot from a google image search)

To Reproduce
Steps to reproduce the behavior:

1. Go to https://crates.io/crates/tide/0.8.1

Expected behavior
The screenshot on the left is much easier for me to read off the information that I care about. The >=A.B.C, <D.E.F ranges are just unnecessarily verbose/cluttered and disguises when there are real >=/< dependencies that are not equivalent to a ^ dependency (as in >=0.2, <0.4). 😕

Additional context
If this was not made as an intentional change, it's possible it was introduced inadvertently in the course of a dependency update such as #2990.

[Turbo87]

I looked into this a little bit, and what happens is that on upload we parse the requirement string into a VersionReq and when we save it into the database we convert it back to a string. Similarly when we read it from the database we parse it into a VersionReq and then convert it back to a string when serializing as JSON.

Unfortunately, the new semver release changed their VersionReq::to_string implementation, which means that we're now converting to these ranges instead of using the ^ prefix in both cases.

From what I can tell we don't use the VersionReq for anything inside our code, so we could probably just save the original strings instead, and add a validation check in the upload route handler.

[Turbo87]

#3051 reverted the semver upgrade for now, so I guess we can close this issue. #3049 will follow up on this by adding regression tests and saving the original version requirement in the database.