createTexture method
A brand-new texture matching spec, with the single TextureHandle that
will ever stand for it.
Implementation
@override
TextureHandle createTexture(RenderTargetSpec spec, {int levels = 1}) => guard(
'a ${spec.width}x${spec.height} ${spec.format.name} target',
() => webgpuCreateTexture(gpuDevice, _textures, spec, levels: levels),
);