[ao] backend_config moving all to top (#88391)
Summary: moved __all__ to top of functions, removed private funcitons
from all
Test Plan: python test/test_public_bindings.py
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Differential Revision: [D41015538](https://our.internmc.facebook.com/intern/diff/D41015538)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/88391
Approved by: https://github.com/jcaip
