Refactor rename doesnt handle renaming static shadowed elements

After https://github.com/dart-lang/sdk/issues/59954 I realized we should do a similar processing for _static_ members:

```dart
class ClassName {
  static final _a = 1;

  void foo(int a) {
    print(_a);
  }
}
```

When refactoring `_a` to `a`, it should add `ClassName.`:

```dart
class ClassName {
  static final a = 1;

  void foo(int a) {
    print(a);
  }
}
```