experimental python embedded for Windows and CUDA 12.8

1. Download all the files in this release (comfyui_portable.exe, comfyui_portable.7z.001 and comfyui_portable.7z.002).
2. Run comfyui_portable.exe to extract a workspace containing an embedded Python 3.12 and fully-installed torch and ComfyUI-Manager.
3. Double click on comfyui.bat inside ComfyUI_Workspace to start the server.