Typed array views should unify with ArrayBufferView

Since typed array views [implement the ArrayBufferView interface](https://www.khronos.org/registry/typedarray/specs/latest/#TypedArray), this should work:

``` haxe
var view:haxe.io.ArrayBufferView = new haxe.io.Float32Array(3)
```

However, although `haxe.io.Float32Array` abstracts `haxe.io.ArrayBufferView` it does not implicitly cast to it. `(new Float32Array(3)).view` works but seems unnecessary.

An example of where this is useful is in the WebGL API where `:ArrayBufferView` is the accepted type for a number of parameters.

I think it'd be worthwhile to add `to ArrayBufferView` (or similar) to the typed array abstracts and look into _maybe_ removing the `.view` field since it should no longer be needed. If you agree I'll create a PR.

(There's also a [public `get_view` field](https://github.com/HaxeFoundation/haxe/blob/development/std/haxe/io/Float32Array.hx#L40) on the typed array views which seems like it should be private?)