vircgroup: introduce virCgroupV2ValidateMachineGroup
vircgroup: introduce virCgroupV2ValidateMachineGroup

When reconnecting to a domain we are validating the cgroup name.
In case of cgroup v2 we need to validate only the new format for host
without systemd '{machinename}.libvirt-{drivername}' or scope name
generated by systemd.

Signed-off-by: Pavel Hrdina <d4772d05997b8abf035041e3b4f4996380ea7e7a@redhat.com>

fabianfreyer/libvirt,andreabolognani/libvirt,nertpinx/libvirt,nertpinx/libvirt,zippy2/libvirt,libvirt/libvirt,eskultety/libvirt,jfehlig/libvirt,olafhering/libvirt,fabianfreyer/libvirt,andreabolognani/libvirt,zippy2/libvirt,eskultety/libvirt,nertpinx/libvirt,olafhering/libvirt,nertpinx/libvirt,eskultety/libvirt,fabianfreyer/libvirt,fabianfreyer/libvirt,crobinso/libvirt,nertpinx/libvirt,jfehlig/libvirt,zippy2/libvirt,andreabolognani/libvirt,olafhering/libvirt,jardasgit/libvirt,jfehlig/libvirt,crobinso/libvirt,jardasgit/libvirt,jardasgit/libvirt,jfehlig/libvirt,crobinso/libvirt,jardasgit/libvirt,eskultety/libvirt,libvirt/libvirt,fabianfreyer/libvirt,libvirt/libvirt,zippy2/libvirt,jardasgit/libvirt,crobinso/libvirt,andreabolognani/libvirt,libvirt/libvirt,eskultety/libvirt,andreabolognani/libvirt,olafhering/libvirt