Consider two models A and B, a many2many field F from A to B and its
inverse relation G from B to A.  When F is modified, G is updated
accordingly in cache.  The statement

    records.write({F: [(4, b.id)]})    # link b to records

is expected to add b.id to records.F, and add records.ids to b.G.  In
order to avoid nondeterminism, the additions should be done at the end
of the recordset, and in order.  In other words, if none of "records"
are in b.G, then after the statement above, b.G should be updated as

    b.G = b.G + records

This patch ensures that "records" are added in order.

closes odoo/odoo#94782

Signed-off-by: Vincent Schippefilt (vsc) <vsc@odoo.com>