Implementation of all expansion and all folding functions

Osumi Yuya

I want to collapse the entire tree to make it easier to see, not collapse the core.
If you can develop them one by one, it will be easier to explain when you share ideas with your peers.

If you add the ability to expand all, you can get it back even after it's all collapsed.
If possible, it would be great if you could right-click and select those functions.