qemu-sbuild-utils merged into sbuild

qemu-sbuild-utils have been merged into sbuild and are now shipped as package sbuild-qemu. The executables have been renamed from qemu-sbuild-* to sbuild-qemu-*, to be consisent with the other utilities provided by sbuild.

I may or may not have botched the transitional dummy package, but as the original package never migrated to testing (this was deliberate) and popcon was low, I'm confident that people will manage.

sbuild-qemu depends on the recently uploaded vdbm2, which added support for arm64, armhf, and ppc64el images. This is really exciting, as this means that sbuild-qemu and autopkgtest will soon be able to build for and test on most of the officially supported architectures, all from one host machine. MRs to enable these new features in autopkgtest have already been filed by Ryutaro Matsumoto. Support for the armel architecture is being discussed; support for the MIPS architectures is a more complicated issue, as they don't use GRUB.

I'd like to thank Johannes Schauer for reaching out, initiating discussion, and collaborating on this merge!