maple_tree: use maple copy node for mas_wr_rebalance() operation

maple_tree: use maple copy node for mas_wr_rebalance() operation

Stop using the maple big node for rebalance operations by changing to more
align with spanning store.  The rebalance operation needs its own data
calculation in rebalance_data().

In the event of too much data, the rebalance tries to push the data using
push_data_sib().  If there is insufficient data, the rebalance operation
will rebalance against a sibling (found with rebalance_sib()).

The rebalance starts at the leaf and works its way upward in the tree
using rebalance_ascend().  Most of the code is shared with spanning store
such as the copy node having a new root, but is fundamentally different in
that the data must come from a sibling.

A parent maple state is used to track the parent location to avoid
multiple mas_ascend() calls.  The maple state tree location is copied from
the parent to the mas (child) in the ascend step.  Ascending itself is
done in the main loop.

Link: https://lkml.kernel.org/r/20260130205935.2559335-23-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Andrew Ballance <andrewjballance@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Christian Kujau <lists@nerdbynature.de>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: SeongJae Park <sj@kernel.org>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>