[cargo] Support for cargo-index

[prabhu]

We can support cargo-cache (and cargo-index) as a project type, similar to maven-index and gradle-index. It would allow organizations to generate a single aggregate pre-build SBOM, after compiling a number of projects. I can also imagine scenarios where Cargo.lock files aren't available, making this a fallback option.

Path to the cache.

$HOME/.cargo/registry/src/index.crates.io-<hash>