texture cache: share color attachment rendering setup

src/graphics/host_gpu/renderer/cache/textureCache.h

@@ -150,6 +150,12 @@ private:
 	// Caller holds m_lock. Volume layer ranges select depth slices.
 	void ClearImage(CommandBuffer& command, ImageId id, vk::Format format,
 	                const vk::ImageSubresourceRange& range, const vk::ClearValue& clear);
+	// Caller holds m_lock and ends rendering. Begins rendering `layers` layers of one color mip
+	// through a `format` view, clearing them or, when `clear` is null, loading them; returns the
+	// render area.
+	vk::Rect2D BeginColorRendering(Image& image, vk::Format format, uint32_t level,
+	                               uint32_t layer, uint32_t layers, const vk::ClearValue* clear,
+	                               vk::CommandBuffer command);
 	void PrepareImageCopy(Image& image);
 	void RefreshCopySource(ImageId id);
 	[[nodiscard]] bool CopyD16(Image& destination, Image& source);