Just during the past week or so a patch version of dev-lang/rust was released:1.67.1

As part of the on-going effort to ensure dev-lang/rust is on track with upstream, in sync with our dev-lang/rust-bin autogen, and ensure Funtoo users have the option to compile the latest dev-lang/rust from source, this improvement task is to track the efforts to bump the lang-kit's dev-lang/rust package to the new patch version and all of the integration testing around it.

Upstream release notes:

• https://blog.rust-lang.org/2023/02/09/Rust-1.67.1.html
• https://blog.rust-lang.org/2023/03/09/Rust-1.68.0.html