[GLCC 2024] support local tarball for nydusify copy

[imeoer]

Support for exporting nydus image blobs into tarball format, and allow import the tarball into local / image registry, which is very useful in some network isolation/no image registry scenarios, similar to the implementation of docker save/load.

Possible implementation steps:

• support nydusify copy --source file:///path/to/image.targz --target $remote-image command to pull an image from the remote registry and save it as a local tarball file, or export the local tarball file to a remote image, please note that both OCI v1 and nydus format should be supported.

[imeoer]

Done.