Polish documentation of manim.utils.color.core and remove interpolate_array()

[chopan050]

EDIT: PR #3999 already typed the entire manim.utils module, including manim.utils.color.core, before I did. Therefore, I changed this PR's name to focus on the other things it does: polish docs and remove interpolate_array().

• Stopped ignoring MyPy errors for manim.utils.color.
• Fixed MyPy errors in manim.utils.color.core.
• Removed the manim.utils.color.core.interpolate_array() function, because manim.utils.bezier.interpolate() already exists and provides the exact same functionality.
• The docs were rewritten a bit to comply more with standards.

Links to added or changed documentation pages

https://manimce--4065.org.readthedocs.build/en/4065/reference/manim.utils.color.core.html

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

[behackl]

I did a coarse reading of the documentation changes and reviewed the typing changes -- thanks for the hard work with the color module, this is a substantial improvement!

Given that the docs seem fine and mypy appears happy, I'm merging this.