Treat parameters-with-newline as empty in function formatting (#7550)

## Summary

If a function has no parameters (and no comments within the parameters'
`()`), we're supposed to wrap the return annotation _whenever_ it
breaks. However, our `empty_parameters` test didn't properly account for
the case in which the parameters include a newline (but no other
content), like:

```python
def get_dashboards_hierarchy(
) -> Dict[Type['BaseDashboard'], List[Type['BaseDashboard']]]:
    """Get hierarchy of dashboards classes.

    Returns:
        Dict of dashboards classes.
    """
    dashboards_hierarchy = {}
```

This PR fixes that detection. Instead of lexing, it now checks if the
parameters itself is empty (or if it contains comments).

Closes https://github.com/astral-sh/ruff/issues/7457.

crates/ruff_python_ast/src/nodes.rs

@@ -2135,6 +2135,15 @@ impl Parameters {
         }
         false
     }
+
+    /// Returns `true` if the [`Parameters`] is empty.
+    pub fn is_empty(&self) -> bool {
+        self.posonlyargs.is_empty()
+            && self.args.is_empty()
+            && self.kwonlyargs.is_empty()
+            && self.vararg.is_none()
+            && self.kwarg.is_none()
+    }
 }
 
 /// An alternative type of AST `arg`. This is used for each function argument that might have a default value.