.cargo/config only respected if in current directory

[jonhoo]

The documentation for Cargo configuration indicates that .cargo/config files may be present at any parent directory of the current project, and that they will all be read and unified. However, at the moment, cargo outdated only copies over .cargo/config if it is in the workspace root: https://github.com/kbknapp/cargo-outdated/blob/d09073947bfc481e861a2dc08a568cefce355c1a/src/cargo_ops/temp_project.rs#L122

That code should be updated to search up the stack, and unify config files as it goes (though it's not clear how that unification works in cargo?).