Fixed closed path ROTATION_MODE_ORIENTED

[Yxure]

Paralell rotation frame does not guarantee that the rotation at the beginning of the curve is equal to that at the end of the curve. This caused that in PathFollows3D with ROTATION_MODE_ORIENTED the rotation changed suddenly at the end of the loop. Added checkbox option to smooth the curve tilt.

_.Test.tscn.-.RotationBezier.-.Godot.Engine.2021-11-19.00-03-15.mp4

Fixes #27137 and part of #47445

[Calinou]

I'm not sure if the auto_tilts property name effectively conveys what it's supposed to do.

Also, does this need to be made optional? Is there a reason as to why someone would want to leave this disabled?

[Yxure]

I got the idea from this paper. Basically it says that you can use this technique to rotate several times around the path. But thinking about it now, it's not very common and it shouldn't be too difficult to code it yourself. I will remove the auto tilts option.