Merge #576 #581 #583

576: Format imports r=stlankes a=mkroening



581: Omit implicit core,alloc from build-std r=mkroening a=mkroening



583: Dockerfile: Update rustup-init to 1.25.1 r=mkroening a=mkroening



Co-authored-by: Martin Kröning <mkroening@posteo.net>