2024-05-01

Prefer pub(crate) for visibility

Summary:
`pub(crate)` generally gives better 'unused definition' warnings from rustc, because it knows the definition isn't used elsewhere.

Use `pub(crate)` wherever we can, and fix definitions that didn't need to be `pub` or `pub(crate)`.

Reviewed By: samkevich

Differential Revision: D56778389

fbshipit-source-id: b73364f96e9601e94a1196b25f78e92968a3edb0