When dropping a node in a different tree, the `nodePerNodeId` of the forest was
not updated. The result was that `HierarchyNode.canShowChildNodes()` could be
wrong because `Forest.resIds` could contain the same id multiple time if the
original tree is unfolded again after the drop operation. Properly calling
`collapseChildNodes` on the root of the expanded tree will update
`nodePerNodeId` for the tree and the forest.
task-3562116
Part-of: odoo/odoo#143941
abd-msyukyu-odoo
c477d21384