Deduplicate setup_dest_layout

The vube and skybox need the layout of their desc_set twice,
once for creating their pipeline, once for creating their desc set,
two different functions were used for that (one of which belonging
to the `WorldComponent` trait), now since they can't be fully merged,
one just calls the other.

src/render/cube.rs

@@ -140,25 +140,7 @@ impl WorldComponent for Cube {
     }
 
     fn desc_layout(&self, ctx: &RenderCtx) -> vk::DescriptorSetLayout {
-        let storage_binding = vk::DescriptorSetLayoutBinding::default()
-            .binding(0)
-            .descriptor_type(vk::DescriptorType::STORAGE_BUFFER)
-            .descriptor_count(1)
-            .stage_flags(vk::ShaderStageFlags::VERTEX);
-        let image_binding = vk::DescriptorSetLayoutBinding::default()
-            .binding(1)
-            .descriptor_type(vk::DescriptorType::COMBINED_IMAGE_SAMPLER)
-            .descriptor_count(1)
-            .stage_flags(vk::ShaderStageFlags::FRAGMENT);
-        let layouts = [storage_binding, image_binding];
-
-        let layout_info = vk::DescriptorSetLayoutCreateInfo::default().bindings(&layouts);
-        let layout = unsafe {
-            ctx.dev
-                .create_descriptor_set_layout(&layout_info, None)
-                .expect("Failed to create descriptor set layout")
-        };
-        layout
+        setup_desc_layout(ctx)
     }
 
     fn write_desc_set(

src/render/skybox.rs

@@ -23,20 +23,7 @@ impl WorldComponent for Skybox {
     }
 
     fn desc_layout(&self, ctx: &RenderCtx) -> vk::DescriptorSetLayout {
-        let image_binding = vk::DescriptorSetLayoutBinding::default()
-            .binding(0)
-            .descriptor_type(vk::DescriptorType::COMBINED_IMAGE_SAMPLER)
-            .descriptor_count(1)
-            .stage_flags(vk::ShaderStageFlags::FRAGMENT);
-        let layouts = [image_binding];
-
-        let layout_info = vk::DescriptorSetLayoutCreateInfo::default().bindings(&layouts);
-        let layout = unsafe {
-            ctx.dev
-                .create_descriptor_set_layout(&layout_info, None)
-                .expect("Failed to create descriptor set layout")
-        };
-        layout
+        setup_desc_layout(ctx)
     }
 
     fn write_desc_set(