Remove useless inheritance from VGroup

[Nikhil-42]

Description

Several of the implemented Mobjects inherit from VGroup. This is typically unnecessary and can lead to strange behavior when using operators. Instead inherit from VMobject or Mobject.

[Nikhil-42]

Make sure to verify that the functionality of the Mobject really doesn't depend on the VGroup inheritance. Namely, look at the methods and operators that VGroup adds (in vectorized_mobject.py) and see if they make sense to keep. For example, it doesn't really make sense that adding an Mobject to an MArrayElement links their positions, rotations, and scale together.