Simplify module visibility post build refactor

//visibility:override is no longer needed for impl_library_visibility
to override visibility.

Removing this allows the defaults module to specify better defaults.

- Stub libraries are made publicly visible, via `visibility`
- Impl libraries are private by default, but visibility is extended
  by the modules

Bug: 165017290
Test: m
Change-Id: Ibd4765f29f5d9c2551062725650722f5a25d7bd6
1 file changed