This overload adds complexity without providing much benefit of clarity.
In all contexts, the semantics of the values in an array used as a
GPUOrigin/Extent are clear; depending on the context, one of:

- [width]
- [width, arraysize]
- [width, height]
- [width, height, arraysize]
- [width, height, depth]

In order to implement this, this redefines GPUOrigin2D, GPUOrigin3D, and
GPUExtent3D from scratch, as if they were specified in the WebIDL spec.
These essentially implement a specific case of tuples with default
values, which could be expressed in pseudo-WebIDL as:

```
typedef [GPUIntegerCoordinate = 0, GPUIntegerCoordinate = 0] GPUOrigin2D;
typedef [GPUIntegerCoordinate = 0, GPUIntegerCoordinate = 0, GPUIntegerCoordinate = 0] GPUOrigin3D;
typedef [GPUIntegerCoordinate, GPUIntegerCoordinate, GPUIntegerCoordinate] GPUExtent3D;
```

I previously proposed this in gpuweb#299. After discussion, we compromised on
this union, and it was implemented in gpuweb#319. However there were a number
of voices who didn't like the added complexity (and perceived loss of
type expressivity), and since then I've come to agree that the unioned
version is not the best choice.

This overload adds complexity without providing much benefit of clarity.
The semantics of the values in an array are clear according to context:

- 1d: [width]
- 1d-array: [width, arraysize]
- 2d: [width, height]
- 2d-array/cube/cube-array: [width, height, arraysize]
- 3d: [width, height, depth]

In order to implement this, this redefines GPUOrigin2D, GPUOrigin3D, and
GPUExtent3D from scratch, as if they were specified in the WebIDL spec.
These essentially implement a specific case of tuples with default
values, which could be expressed in pseudo-WebIDL as:

```
typedef [GPUIntegerCoordinate = 0, GPUIntegerCoordinate = 0] GPUOrigin2D;
typedef [GPUIntegerCoordinate = 0, GPUIntegerCoordinate = 0, GPUIntegerCoordinate = 0] GPUOrigin3D;
typedef [GPUIntegerCoordinate, GPUIntegerCoordinate, GPUIntegerCoordinate] GPUExtent3D;
```

I previously proposed this in gpuweb#299. After discussion, we compromised on
this union, and it was implemented in gpuweb#319. However there were a number
of voices who didn't like the added complexity (and perceived loss of
type expressivity), and since then I've come to agree that the unioned
version is not the best choice.

This overload adds complexity without providing much benefit of clarity.
The semantics of the values in an array are clear according to context:

- 1d: [width]
- 1d-array: [width, arraysize]
- 2d: [width, height]
- 2d-array/cube/cube-array: [width, height, arraysize]
- 3d: [width, height, depth]

In order to implement this, this redefines GPUOrigin2D, GPUOrigin3D, and
GPUExtent3D from scratch, as if they were specified in the WebIDL spec.
These essentially implement a specific case of tuples with default
values, which could be expressed in pseudo-WebIDL as:

```
typedef [GPUIntegerCoordinate = 0, GPUIntegerCoordinate = 0] GPUOrigin2D;
typedef [GPUIntegerCoordinate = 0, GPUIntegerCoordinate = 0, GPUIntegerCoordinate = 0] GPUOrigin3D;
typedef [GPUIntegerCoordinate, GPUIntegerCoordinate, GPUIntegerCoordinate] GPUExtent3D;
```

I previously proposed this in gpuweb#299. After discussion, we compromised on
this union, and it was implemented in gpuweb#319. However there were a number
of voices who didn't like the added complexity (and perceived loss of
type expressivity), and since then I've come to agree that the unioned
version is not the best choice.

* Allow marking tests as explicitly unimplemented

This allows for test structure to be committed into the CTS before the
tests themselves are implemented.

* Make the testCreationStack slightly nicer