Simplify `children_and_closing` interface
Simplify `children_and_closing` interface

Summary: Callers should not need to pass in the `acc`. This cleans up the interface a bit. Mainly though, this makes a change in the next diff a little bit simpler.

Reviewed By: dsainati1

Differential Revision: D14014534

fbshipit-source-id: db2c9566351fe621f20bc6480462bb41b6af7104

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