nydusify: introduce copy subcommand #1762

Job	Run time
contrib-build	3m 46s
contrib-build-master	4m 30s
nydus-build	2m 59s
nydus-build-master	2m 33s
cargo-deny	3m 24s
nydus-unit-test	7m 23s
nydus-unit-test-coverage	3m 35s
benchmark-oci	1m 32s
benchmark-nydus-all-prefetch	1m 6s
benchmark-nydus-no-prefetch	38s
benchmark-nydus-filelist-prefetch	3m 31s
benchmark-zran-all-prefetch	1m 32s
benchmark-zran-no-prefetch	1m 10s
nydus-integration-test	11m 53s
benchmark-nydus-filelist-prefetch-master	3m 18s
benchmark-nydus-all-prefetch-master	55s
benchmark-nydus-no-prefetch-master	40s
benchmark-zran-all-prefetch-master	1m 26s
benchmark-zran-no-prefetch-master	1m 14s
benchmark-result	0s
benchmark-compare	9s
	57m 14s

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