p-tree: Unselectable children when no key given in TreeNode

[SuRaMoN]

Describe the bug

Caused by: #16430

This fix causes nodes to be unselectable when nodes do not have a key.

example:
https://stackblitz.com/edit/github-fos6jj-ljajyw?file=src%2Fapp%2Fapp.component.ts

Screen recording (i'm clicking the nodes, but they dont get selected):

If you remove the keys sicne this fix selection does not work, with keys, it does work.

Reason is that since this fix we are cloning nodes:

But without keys we do a full contents comparison that always fails:

Environment

https://stackblitz.com/edit/github-fos6jj-ljajyw?file=src%2Fapp%2Fapp.component.ts

Reproducer

https://stackblitz.com/edit/github-fos6jj-ljajyw?file=src%2Fapp%2Fapp.component.ts

Angular version

17.3.6

PrimeNG version

17.18.11

Build / Runtime

Angular CLI App

Language

TypeScript

Node version (for AoT issues node --version)

18.20.3

Browser(s)

No response

Steps to reproduce the behavior

Create a p-tree with checkboxes and TreeNodes without key
Click on a checkbox of the tree
https://stackblitz.com/edit/github-fos6jj-ljajyw?file=src%2Fapp%2Fapp.component.ts

Screen recording (i'm clicking the nodes, but they dont get selected):

Expected behavior

The treenodes should be selectable even when they have no key as was the case before #16430 was merged

[github-actions]

Due to PrimeNG team's busy roadmap, this issue is available for anyone to work on. Make sure to reference this issue in your pull request. ✨ Thank you for your contribution! ✨