feat: --stream-layers for streaming weights from CPU during generation (#1576)

src/upscaler.h

@@ -18,6 +18,7 @@ struct UpscalerGGML {
     bool direct                 = false;
     int tile_size               = 128;
     size_t max_graph_vram_bytes = 0;
+    bool stream_layers_enabled  = false;
     std::string backend_spec;
     std::string params_backend_spec;
 
@@ -31,6 +32,7 @@ struct UpscalerGGML {
                         bool offload_params_to_cpu,
                         int n_threads);
     void set_max_graph_vram_bytes(size_t max_vram_bytes);
+    void set_stream_layers_enabled(bool enabled);
     sd::Tensor<float> upscale_tensor(const sd::Tensor<float>& input_tensor);
     sd_image_t upscale(sd_image_t input_image, uint32_t upscale_factor);
 };