spec: move driver-specific files to driver subpackages

spec: move driver-specific files to driver subpackages

The libvirt-daemon package contains several driver-specific files,
directories, and script, which can be problematic when building the
package with multiple hypervisor support, e.g. both QEMU and Xen.

E.g. installing a QEMU+Xen enabled libvirt-daemon on a Xen-only system
will result in the creation of qemu and kvm groups and a qemu user.

Move the driver-specific files, directories, and script to the
respective driver subpackages.