Easily inspect dependencies

Cargo should provide a way for users to trivially find and/or open locally-cached crates. The current UX discourages cding or opening deps:

# using Rust fmt-str syntax
open ".cargo/registry/src/index.crates.io-{HEX_NONSENSE}/{NAME}-{VERSION}/src/foobar.rs"

Today, the only easy way is to use rust-analyzer with goto-def, but that's overkill in many cases, and sometimes prohibitively computationally expensive.

This isn't just an ergonomics issue, it's a security issue.

I've recently read about cargo vendor, but it's not a proper solution, IMO