TreeCell: cell editing state not updated on cell re-use

similar to pre-fix of JDK-8150525, the cell's editing property is not updated when updating its index, examples of failing tests:

    int editingIndex = 2;
    int cellIndex = 1;
     @Test
    public void testOffEditingIndex() {
        cell.updateIndex(editingIndex);
        TreeItem<String> editingItem = table.getTreeItem(editingIndex);
        table.edit(editingItem);
        cell.updateIndex(cellIndex);
        assertEquals("sanity: cell index changed", cellIndex, cell.getIndex());
        assertFalse("cell must not be editing on update from editingIndex" + editingIndex
                + " to cellIndex " + cellIndex, cell.isEditing());
    }
   
    @Test
    public void testToEditingIndex() {
        cell.updateIndex(cellIndex);
        TreeItem<String> editingItem = table.getTreeItem(editingIndex);
        table.edit(editingItem);
        cell.updateIndex(editingIndex);
        assertEquals("sanity: cell at editing index", editingIndex, cell.getIndex());
        assertTrue("cell must be editing on update from " + cellIndex
                + " to editingIndex " + editingIndex, cell.isEditing());
    }
    
fix might be similar like that for TableCell (force updateEditing always) - doing so still leaves some unhandled transitions. Needs further digging.