Like Ruby did in #12566

Screenshots show last step before reaching the final sink (foo in eval(foo))

OLD

NEW

I don't know why we're still seeing the attribute read step though, like the one from the request in request.args.get("name") to request.args. I had actually thought they would go away when removing readStep(_, _, n) from neverSkipInPathGraph. I don't think these steps are very useful, since they're both part of the same statement, so would be nice to be able to get rid of them 😅

I used DefinitionNode since that would easily allow me to use the RHS of both normal assignments and augmented assignments (+=), but I'm not entirely sure if it has precisely the right logic around tuple assignments... will have to check that out in more detail!

(draft PR because I expect a lot of .expected files to need updating)