[meta-virtualization] image-oci.bbclass: description of usage of oci image

Hi Bruce
    1.  I follow the step of running oci image in  image-oci.bbclass but it has error in runc.

    # tar -xvf container-base-latest-oci-dir.tar                                                                      
                                                                   
    # oci-image-tool create --ref name=latest container-base-qemux86-64.rootfs-20260302090735.rootfs-oci container-base-oci-bundle                                                                        
                                                                      
    # runc run -b container-base-oci-bundle ctr-build                                                                       
ERRO[0000] runc run failed: unable to start container process: error during container init: open /dev/pts/ptmx: no such file or directory                                                                   

  2. Then I follow the comment in image-oci-umoci.inc using two methods which can run container successfully
    # make a tar version of the image direcotry
    #  1) image_name.tar: compatible with oci tar format, blobs and rootfs
    #     are at the top level. Can load directly from something like podman
    #  2)image_name-dir.ta: original format from meta-virt, is just a tar'd
    #     up oci image directory (compatible with skopeo :dir format)

   2.1 Method 1 for image_name.tar
# podman load -i container-base-latest-oci.tar

# podman images | grep localhost/latest
localhost/latest                           latest      1d603a1041c5  14 years ago   5.58 MB

# podman run -it 1d603a1041c5
/ # ls
bin    boot   dev    etc    home   lib    media  mnt    proc   root   run    sbin   sys    tmp    usr    var

    2.2  Method 2 for image_name-dir.tar
# tar xvf container-base-latest-oci-dir.tar
# skopeo copy oci:container-base-qemux86-64.rootfs-20260302090735.rootfs-oci:latest containers-storage:container-base-qemux86-64:1.0
# podman images | grep container-base-qemux86-64
docker.io/library/container-base-qemux86-64  1.0         1d603a1041c5  14 years ago   5.58 MB

# podman run --rm -it 1d603a1041c5
/ # ls
bin    boot   dev    etc    home   lib    media  mnt    proc   root   run    sbin   sys    tmp    usr    var

       Based on this phenomenon, I think we can modify the  description of usage of oci image in image-oci.bbclass to use the  two methods above.

       What do you think about my suggestion？

Liu