Currently the cognitive complexity lint spans the entire function
body making it really difficult to read and refactor the code in
editors. To fix this we reduce the lint span to the function name.
* Ran automatic naming update
* Formalized rename of `cyclomatic_complexity` to `cognitive_complexity`
** Added the rename to `lib.rs`
** Added rename test
* Added warning for deprecated key `cyclomatic_complexity_threshold` and tests for it
* Added deprecation status for Clippy's builtin attribute
* Updated tests for new builtin attribute renaming
