Reduce the time for CLI startup

[naveen521kk]

Description of the proposed feature

Currently, when running manim executable or module using (py -m manim), the whole module is imported which is large and takes a lot of time. I propose to move all the CLI handling stuff (ie manim.cli) to a new module called manim_cli which would not import manim until the command line arguments are parsed. By doing so, we can reduce the startup time.

How can the new feature be used?

Reduce the time to load manim command. If someone just wanted to see the help this would reduce the time they wait because manim wouldn't be imported in that case.

Additional comments

We would need to move the main module to src structure for this to work.

src \
    - manim
    - manim_cli

[Freyert]

@naveen521kk is there any explanation as to why manim cli currently imports all the entire library? I would expect rendering a scene to only require the libraries imported in the user's python. Not the entire library.

[naveen521kk]

is there any explanation as to why manim cli currently imports all the entire library?

It's been like that forever. Someone should change it.