Rewrite `yield-in-for-loop` to avoid recursing over body (#6692)
## Summary
This is much simpler and avoids (1) multiple passes over the entire
function body, (2) requiring the rule to do its own binding tracking (we
can just use the semantic model), and (3) a usage of `StatementKey`.
In general, where we can, we should try to remove these kinds of custom
visitors that track name references, and instead rely on the semantic
model.
## Test Plan
`cargo test`
