FROMGIT: maple_tree: add test for mtree_dup()

Add test for mtree_dup().

Test by duplicating different maple trees and then comparing the two
trees.  Includes tests for duplicating full trees and memory allocation
failures on different nodes.

Link: https://lkml.kernel.org/r/20231027033845.90608-6-zhangpeng.00@bytedance.com


Signed-off-by: Peng Zhang <zhangpeng.00@bytedance.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Mike Christie <michael.christie@oracle.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

(cherry picked from commit a2587a7e
https://git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

 mm-unstable)

Bug: 308042511
Change-Id: I7501db5735b1dfd15240ef2946b26d63ffe1d8e0
Signed-off-by: Suren Baghdasaryan <surenb@google.com>