Provide a better description on what does "navigation_finished" and "target_reached" signals do on NavigationAgent3D

[enxas]

Your Godot version:
4.1

Issue description:
"navigation_finished" and "target_reached" signal descriptions make it seem like they both do the same thing, which is fire when target is reached. What are the differences? Why would I use one over the other?

URL to the documentation page (if already existing):
https://docs.godotengine.org/en/4.1/classes/class_navigationagent3d.html

[smix8]

See descriptions in the linked pr.

This node documentation is part of the class doc which is part of the main godot repo, not the godot-docs repo.