Fix default NodePaths saved in scene

[KoBeWi]

Fixes #91591

I spent whole day writing tests for both #91591 and #82670
In the end it turned out that disabling #83343, or at least part of it, fixes both issues. I don't know what to think about it, maybe I'm missing something.

Putting as draft. If it's a correct solution I assume more code needs to be removed.

[Cronos87]

Maybe it would be good to ask @warriormaster12 to try this MR; it could help to make progress on it?

That would be beneficial to prevent regression on #83343.

[warriormaster12]

I can certainly give it a look however I'm not sure if I'm going to be able to give any useful input on the matter since my understanding of the code is as much as I touched.

[warriormaster12]

Hmm the assumption that I made in property_utils.cpp in regards of affecting duplication was wrong. Duplicating a node still works even without if check. The only thing that changes is an ability to revert exported Node values in my_level.tscn provided by @Cronos87. Reverting them does nothing. Other variable types don't allow you to revert values in an instantiated scene unless a user has changed the values.

However, if this only causes a cosmetic inconsistency then I don't see an issue in reverting the change.

[KoBeWi]

Pushed a solution that doesn't break reverting.

[akien-mga]

Thanks!

[Cronos87]

Many thanks for the fix and review! 🙏