Auto merge of #45948 - Mark-Simulacrum:beta-next, r=alexcrichton
Beta next
This updates beta Cargo (brings https://github.com/rust-lang/cargo/pull/4716 and https://github.com/rust-lang/cargo/pull/4715), and also includes https://github.com/rust-lang/rust/pull/45866.
This PR also bumps beta to .3 so that we can get a beta release soon.