cravex2-reachability: Vulnerable code "reachability" determination

We should extend the basic vulnerable code symbol-based "reachability" to determine if the code impacted by a CVE is present, used and exploitable. We should also integrate and extend the reachability-related features of existing FOSS projects, such as BANG, atom and chen.

- See many references are in https://github.com/aboutcode-org/vulnerablecode/issues/1313