snapshotter: support "remap-ids" capability for overlayfs

Previously remapping of a snapshotter has been done using
recursive chown.

Commit
31a6449734 added a support
for "remap-ids" capability which allows snapshotter internals do
remappings in case of idmapped mounts support to avoid recursive
chown and creating a new remapped snapshot.

Signed-off-by: Ilya Hanov <ilya.hanov@huawei-partners.com>

snapshots/overlay/overlayutils/check.go

@@ -198,3 +198,14 @@ func NeedsUserXAttr(d string) (bool, error) {
 	}
 	return true, nil
 }
+
+// SupportsIDMappedMounts tells if this kernel supports idmapped mounts for overlayfs
+// or not.
+func SupportsIDMappedMounts() (bool, error) {
+	// Fast path
+	fiveDotNineteen := kernel.KernelVersion{Kernel: 5, Major: 19}
+	if ok, err := kernel.GreaterEqualThan(fiveDotNineteen); err == nil && ok {
+		return true, nil
+	}
+	return false, nil
+}