Move inc to cmd/inc #41

Job	Run time
Documentation tests	9m 12s
Code tests	9m 0s
Client tests (1.18.x, ubuntu-latest)	52s
Client tests (1.18.x, macos-latest)	1m 8s
Client tests (1.18.x, windows-latest)	1m 11s
System tests (1.18.x, cluster, dir)	13m 15s
System tests (1.18.x, cluster, btrfs)	13m 49s
System tests (1.18.x, cluster, lvm)	15m 35s
System tests (1.18.x, cluster, zfs)	15m 35s
System tests (1.18.x, cluster, ceph)	19m 29s
System tests (1.18.x, cluster, random)	14m 20s
System tests (1.18.x, standalone, dir)	23m 35s
System tests (1.18.x, standalone, btrfs)	22m 52s
System tests (1.18.x, standalone, lvm)	39m 30s
System tests (1.18.x, standalone, zfs)	45m 18s
System tests (1.18.x, standalone, ceph)	1h 14m 14s
System tests (1.18.x, standalone, random)	33m 46s
System tests (stable, cluster, dir)	13m 10s
System tests (stable, standalone, dir)	24m 58s
System tests (tip, cluster, dir)	15m 37s
System tests (tip, standalone, dir)	26m 49s
	7h 13m 15s

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