Fixes#85032
The code that fix the issue is courtesy of @Jesusemora, I just added
unit tests for it and did a rebase with the latest changes on master.
Co-authored-by: Jesusemora <32273722+Jesusemora@users.noreply.github.com>
Added TreeItem::last_child to avoid needing to iterate through all children to get to the end. This mainly helps in cases where one TreeItem has many children (1000s), and new children are added to the end, as each add had to iterate through all previously added children.
