Switch expression is not exhaustive on integers

* Dart 3.0.0

The analyzer claims that the following code snippet isn't exhaustive when it is. It emits the following message: `The type 'int' is not exhaustively matched by the switch cases since it doesn't match 'int()'`.

```dart
void main() {
final foo = switch ('a'.compareTo('b')) {
> 0 => 'more',
== 0 => 'equal',
< 0 => 'less',
};
}
```

No implementation file or test is named. Start by reproducing the Dart 3.0.0 switch expression from the issue and trace the analyzer's exhaustiveness check for relational patterns on int; done means the exhaustive cases no longer produce the reported int() diagnostic.

Written by the indexing model from the issue text.