Add support for negative z-index in AnimationGroup

[Merzlikin-Matvey]

Overview: What does this pull request change?

Fixes an AnimationGroup behaviour with negative z_index Mobjects. More about this problem you can see in these issues: https://github.com/ManimCommunity/manim/issues/3334 and https://github.com/ManimCommunity/manim/issues/3914

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

Mobjects with negative z_index have problems with playing in animations. This PR fixes it

Links to added or changed documentation pages

There are no changes to the documentation

Further Information and Comments

I had already opened a pull request, but I decided to close it due to many issues with the previous solution. I have taken all the shortcomings, now there are no performance or graphical test issues.

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