Fix and clean up Build-Depends

• d/control: Drop versions from Build-Depends that are satisfied since buster.

  This reduces the amount of information duplicated by the next commit.

• d/control: Fix profiles for Build-Depends on bison, cpio, flex, xz-utils.

  These are each needed unless two different build profiles are specified, which wasn't expressed correctly.

• d/control: Move bison, cpio, flex, xz-utils to Build-Depends-{Arch,Indep}.

  This makes it a bit clearer why they're needed and reduces the dependencies slightly for an arch-only/indep-only build with some profiles.