Clean up the publicly exported API

[dakinggg]

Fixes up a bunch of __all__s

[mvpatel2000]

Can we please add the trailng commas thing? @b-chu has instructions (reisort)

[b-chu]

Is there a way to automate fixing the all? I think that type of debt will accumulate and require future PRs like this if there's no pre-commit hook for it

[b-chu]

For trailing commas, this is the relevant change to pyproject.toml
https://github.com/mosaicml/composer/pull/3078/files#diff-50c86b7ed8ac2cf95bd48334961bf0530cdc77b5a56f852c5c61b89d735fd711

[dakinggg]

@mvpatel2000 Brian said it wasn't as simple as just changing the pyproject and would take a few hours, so I am not going to include that in this PR

@b-chu Not sure if there is a way to automate the alls. Some of the choices of what to reexport are more subjective, but if there is a good way to automate, I'm very open to it.

[mvpatel2000]

@mvpatel2000 Brian said it wasn't as simple as just changing the pyproject and would take a few hours, so I am not going to include that in this PR

Can we prioritize doing this soon? it has frequently come up in PR reviews