Extend the Texture asset type to support 3D data

[bonsairobo]

Textures are still loaded from images as 2D, but they can be reshaped according to how the render pipeline would like to use them.

Also add an example of how this can be used with the texture2DArray uniform type.

[bonsairobo]

I also think it would be nice to replace the Texture::size field with the Extent3d type, instead of using Vec3. Then you get unsigned integers which are more fit for use.

[bonsairobo]

One thing I am surprised by: I didn't have to change the TextureViewDescriptor for this to work. Right now, it's just constructed using Default, leaving the TextureViewDimension empty. I would've expected it to be necessary to set that to D2Array. But maybe it's just a hint.

[joshuajbouw]

Please run cargo fmt, clean had failed.

[bonsairobo]

Just failing to install udev now.

[cart]

A rebase should do the trick.

I like all of these changes. My biggest question mark is "should we have 2d variants of methods on Texture or just let everyone contend with the fact that its 3d now?"

Its not that much harder to deal with and it keeps the api surface smaller. I have a slight bias toward removing the 2d variants (with the exception of aspect_2d())

[bonsairobo]

@cart I think I am fine with removing the 2d methods, except aspect, like you said.

What do you think about replacing the Vec3 with Extent3d?

[cart]

Yeah I'm cool with that.