Tomasz Chabora

Oof. I just pushed a commit that removes `get_undo_redo2()` and changes the base method to return `Ref`. The amount of changes I had to do in different editors is insane....

I think I'm close to finishing this. After my latest changes it's possible to revert a scene without destroying whole undo history: 

I think I'm done. This ended up being bigger than planned (what a surprise...), but I covered all usages of UndoRedo, hopefully. Obviously all needs testing now. What can break...

> Do you want me to test for a few days using it? That would be helpful. I'm also going to do so. > Any special notes on EditorUndoRedoManager for...

Status update on this PR: I think this is mostly finished now. I have one unresolved problem, but it's not a blocker. Basically I can't forward-declare EditorUndoRedoManager in `editor_inspector.h`. It...

I just pushed a commit that finally implements proper timestamps (so the history behaves in more predictable way), but for some reason undo will stop working randomly. Need to fix...

I squashed the commits because (guess what) rebasing 40 commits is a pain.

Any ideas why this doesn't compile? [0001-fd.patc.txt](https://github.com/godotengine/godot/files/9106999/0001-fd.patc.txt) For whatever reason I can't forward-declare EditorUndoRedoManager in Editor Inspector. It results in "use of undefined type" bug, but I'm not using it;...

Rebased again. I've been using this for the past few weeks. I got 2 crashes at the beginning, but then they never happened again and the undo is reliable. So...

The issue from sanitizers is probably the one responsible for the crash on exit. Not sure what is causing it though.