Making ast.walk 220x Faster

In our AI reflex-app builder we generate massive amounts of Python code. Sometimes, this code generation fails in rather trivial manners; positional parameters after keyword ones, returns with values in async generators, using outdated syntax conventions from previous versions of our framework, etc.

Running reflex compile will eventually find all of those bugs, but it only finds one issue at a time. That means if the AI made multiple mistakes, we are increasing the latency massively for what could be relatively simple fixes.

As such, we decided using a linter would be the best approach to fix this. And since we need to add reflex-specific rules, we couldn't use an existing one, and had to build our own.