We should track a translucent flag on impeller::Texture which only gets set to false by the Impeller image decoder if the texture is known to be completely opaque. Knowing this info at command encoding time would allow us to land many small optimizations centered around blending and draw order.

Currently we use Skia to decompress images, and so we'd need to fetch this info from Skia or ask Skia to track this info + expose it over the public API if not available. We can also partially infer this through the absence of an alpha channel on the input image.