Disable prefab publishing if REACT_NATIVE_HERMES_SKIP_PREFAB is set. (#33439)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/33439

This allows us to toggle the publishing of prefab if the `REACT_NATIVE_HERMES_SKIP_PREFAB`
env variable is set. With this we can control how big is the .aar of hermes-engine, reducing
the size from ~200Mb right now to 8Mb.

Changelog:
[Internal] [Changed] - Disable prefab publishing if REACT_NATIVE_HERMES_SKIP_PREFAB is set

Reviewed By: ShikaSD

Differential Revision: D34929265

fbshipit-source-id: eb710b72ee4e17ac04c2924ffdac7a542928e9f8