[dom ast] case statement rewrite formatting

Consider the following code:

```
public class X {
static int foo(int i) {
int tw = 0;
switch (i) {
case 1 : {
int z = 100;
break;
}
default : {
break;
}
}
return tw;
}
public static void main(String[] args) {
System.out.print(foo(1));
}
}
```

Now add case 100: with a block having a singleton break;

The resulting code looks like:

```
public class X {
static int foo(int i) {
int tw = 0;
switch (i) {
case 1 : {
int z = 100;
break;
}
case 100:
{
break;
}
default : {
break;
}
}
return tw;
}
public static void main(String[] args) {
System.out.print(foo(1));
}
}
```

The case 100: block format is different.

Ref: https://bugs.eclipse.org/bugs/show_bug.cgi?id=545439