Enhance Autocompletion for `mobject.animate.` to Display `Mobject` Methods (#2342)

* Improve autocompletion for mobject.animate to show Mobject methods

- Added type hint `-> _AnimationBuilder | Self` to `Mobject.animate`, enabling autocompletion for `Mobject` methods after `mobject.animate`.

- Prioritized `typing_extensions.Self` over `typing.Self` in imports, so autocompletion of `Mobject` methods also works in Python < 3.11.

* Support `mobject.animate.` autocompletion in IPython

* Add docstring to `__dir__` and add return type hint

* improve docsting `__dir__` _AnimationBuilder