Function webrender::renderer::upload::copy_from_staging_to_cache_using_draw_calls

fn copy_from_staging_to_cache_using_draw_calls(
    renderer: &mut Renderer,
    stats: &mut UploadStats,
    batch_upload_textures: &[Texture],
    batch_upload_copies: Vec<BatchUploadCopy>,
)

Generate and submit composite shader batches to copy from the staging textures to the destination cache textures.

If this shows up in GPU time ptofiles we could replace it with a simpler shader (composite.glsl is already quite simple).