[META] Broader language support / modularization of program analysis pipeline

[JosiahOne]

Think about how to add support for new languages. Ideally this shouldn't require tons of re-work and we should be able to re-use part of what we have.

We could even consider relying fully on other systems to do parts of the pipeline. e.g. semgrep can dump ASTs for many languages. Control flow graph generation is extra tricky and I haven't yet seen a single mechanism for doing this across languages.