extra block backend modules for qemu-system and qemu-utils

 QEMU is a fast processor emulator: currently the package supports Alpha, ARM,
 CRIS, i386, LoongArch, M68k (ColdFire), MicroBlaze, MIPS, PowerPC, RISC-V,
 S390x, SH4, SPARC, x86-64, Xtensa and other emulations. By using dynamic
 translation it achieves reasonable speed while being easy to port on new host
 CPUs.
 .
 This package provides extra block device backend modules for qemu-system
 emulation and qemu-img from qemu-utils package, which are rarely used and
 has extra dependencies.