convert array test to unittest
Drop multielement array construction from single element

This fixes construction of single-element array from non-copyable:

```
record NonCopyable ( ... );

main() {
    var b = array(NonCopyable());
}
```

Array constructor removed:

```
[T,n]
overload Array[T,n](elt: T): returned:Array[T,n]
```

It is over-overloading that causes problems like this.