AsynchronousRemove defers removal of filesystem content until
the Cleanup method is called. Removals will make the snapshot
referred to by the key unavailable and make the key immediately
available for re-use.
NewSnapshotter returns a Snapshotter which uses overlayfs. The overlayfs
diffs are stored under the provided root. A metadata file is stored under
the root.
Supported returns nil when the overlayfs is functional on the system with the root directory.
Supported is not called during plugin initialization, but exposed for downstream projects which uses
this snapshotter as a library.