Generate Yul SSA CFG

[r0qs]

This PR implements a direct translation from Yul AST into a CFG in the SSA form. The implementation is based on the following paper: https://c9x.me/compile/bib/braun13cc.pdf

[matheusaaguiar]

I know it's a draft, but I got curious and started looking at the code and reading the paper yesterday 😅

[ekpyron]

I've not reviewed this properly, but this is not critical for now and (together with the next PR) will be tested by the GreY project, while otherwise still not being public interface, so I'm approving and we can merge and then refine later when we move to actual codegen on top of it to properly test it.