Ssort

Adds support for detecting bindings created using the walrus operator

Improve sorting of class level statements.

Fix nondeterminism in order of resolution failure warning

Change logging to print out a warning for all unresolved requirements, not just the first.

Add support for list arguments to `del` statement.

Recognize class scoped builtins (`__module__` and __qualname__`).

Greatly improves logging in both mutate and check modes.

Adds `raw_input` to the list of builtins.

Fixes black compatibility by no longer adding newlines to empty files.