Improve docs and typings for mobject_update_utils, and add examples for always(), f_always() and cycle_animation()

[chopan050]

Overview: What does this pull request change?

• Added missing docstrings for always(), cycle_animation() and assert_is_mobject_method().
• Improved existing docstrings by including missing Parameters, Returns and Raises sections.
• Added examples for always(), f_always() and cycle_animation().
• Defined a MobjectT TypeVar in order to get better typings for the Mobjects returned by functions such as always_redraw(). For example, if the lambda function inside always_redraw() returns a Brace, the Mobject returned by always_redraw() is now recognized as a Brace and, as such, autocompletion includes Brace methods and attributes.
• Completed typings where Callables were missing parameter and return types.
• Removed unused **kwargs from turn_animation_into_updater() and cycle_animation().

Links to added or changed documentation pages

https://manimce--3976.org.readthedocs.build/en/3976/reference/manim.animation.updaters.mobject_update_utils.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

[chopan050]

I'll mark this as a draft for now. PR #4382 was submitted recently, which made me notice some flaws in the current implementation. Back in the time, I didn't stop ignoring MyPy errors for mobject_update_utils.py and, when I removed it from mypy.ini, many errors appeared that don't have an easy solution. I'll take a deeper look into them later.