Bump the `rand` crate to 0.10?

[woodruffw]

Hi there!

I'm working on dedupling some of uv's resolutions, and one of our last resolutions of rand@0.9 is via quinn-proto. Would you all be open to bumping your bound to rand@0.10?

If so, I'm happy to send a PR with that bump (including any internal API changes needed) 🙂

[djc]

I did start on it:

• Upgrade to rand 0.10 #2531

Not sure it can be part of 0.11.x in terms of semver? (main currently targets 0.12.)

If you want to take what I've got and run with it based on the PR feedback, that would be great!

[woodruffw]

Thanks @djc, I can take a look at your branch and try and build off it! Sorry for missing it originally.

[ww-oai]

Okay, #2643 is my stab at this! I've built it on top of #2531; I've marked it ready for review but I've also noticed that there's still a transitive dep on rand@0.9. I'll work on that.

[woodruffw]

Thank you @djc and @Ralith!