## Summary
This change begins to resolve#16071 by moving the `OperatorPrecedence`
structs from the `ruff_python_linter` crate into `ruff_python_ast`. This
PR also implements `precedence()` methods on the `Expr` and `ExprRef`
enums.
## Test Plan
Since this change mainly shifts existing logic, I didn't add any
additional tests. Existing tests do pass.
Junhson Jean-Baptiste