Move configure_pygui into a Scene method and remove manim.gui

[chopan050]

Overview: What does this pull request change?

I took the manim.gui.gui.configure_pygui function, which is used in Scene.interactive_embed(), and transformed it into a Scene method. Since that function was the only thing in manim.gui, I deleted this module as well.

Motivation and Explanation: Why and how do your changes improve the library?

• configure_pygui was only used by Scene.interactive_embed().
• Its parameters were:
  • A renderer, although configure_pygui only accesses the scene referenced by the renderer, so why not just pass the scene itself instead...?
  • A sequence of widget configurations. Scene.interactive_embed() is the only code which calls configure_pygui and it passes the Scene.widgets to it, so, again, the reference to the scene is enough.
  • A bool.
• Internally, configure_pygui also accesses the Scene.queue of actions to do during Scene.interact(). This Scene is the referenced by the passed renderer... so, again, just pass the scene instead.
• It depends on whether dearpygui is imported, in which case dearpygui_import = True. Otherwise, dearpygui_import = False. This exact same thing also already happens in manim.scene.scene.

Because of the reasons above, I believe that this belongs better as a method of Scene. No need to pass a renderer (or scene), nor a list of widgets, because self is a Scene which already has the widgets attribute, as well as the queue.

Links to added or changed documentation pages

Further Information and Comments

Reviewer Checklist

• The PR title is descriptive enough for the changelog, and the PR is labeled correctly
• If applicable: newly added non-private functions and classes have a docstring including a short summary and a PARAMETERS section
• If applicable: newly added functions and classes are tested