Refactor EditorNode get icon

[YYF233333]

Add a fast path for built-in class in EditorNode::get_class_icon.

#78645 MRP with 28K objects now runs smoothly, 91K objects still sucks.

Would be good if someone knows what EditorNode::get_object_icon does could refactor these code.

Refactor get icon logic.

• Split _get_class_or_script_icon into _get_class_icon and _get_script_icon.
• Change get_class/object_icon to avoid multiple checking.
• Use file extension to identify resource path. This should be cheaper than ResourceLoader::exists.

Test with test_custom_icon.zip, class_name and @icon seems to work without problem. And the performance boost remains true.

[777joe]

Tried this out. This fixes #98666 too.

[Calinou]

Tested locally, it works as expected. It's faster overall but due to remaining bottlenecks, scrolling large Trees is still sluggish, especially when near the bottom.

Code looks good to me.

All tests done with an optimized editor build with theMRP from #78645.

I've also tried the MRP of this PR with 16,384 nodes (duplicated from the original 4 nodes) but couldn't spot much of a performance difference when scrolling.

Local

master

master_local.mp4

This PR

pr_local.mp4

Remote

Stutters due to Tree updates being performed every second are still present.

master

master_remote.mp4

This PR

pr_remote.mp4

[KoBeWi]

This looks mostly like a cleanup, while #101489 is a complete solution. The key point is avoiding to load scripts.

Still, it does not have problems I mentioned in #101489 (comment), and if it's indeed faster, then it's fine for now. The two PRs don't seem mutually exclusive.