Inline method should wrap string interpolations with `{}` when necessary

[stereotype441]

Starting with the following code:

class C {
  final List<String> myList;

  C(this.myList);

  String get _first => myList.first;

  test() => 'The first entry is $_first';
}

main() {
  print(C(['x']).test()); // prints `The first entry is x`
}

Active the "inline method" refactoring on the method _first.

Expected result:

class C {
  final List<String> myList;

  C(this.myList);

  test() => 'The first entry is ${myList.first}';
}

main() {
  print(C(['x']).test()); // prints `The first entry is x`
}

Observed result:

class C {
  final List<String> myList;

  C(this.myList);

  test() => 'The first entry is $myList.first';
}

main() {
  print(C(['x']).test()); // prints `The first entry is [x].first`
}

[scheglov]

https://dart-review.googlesource.com/c/sdk/+/402587