Prevent users from opting-out of the New Architecture (#53026)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/53026

This change prevents users from opting out of the New Architecure.

The change is non breaking with respect to building an app: all the functions are still there, even if they are unreachable, in case users will still call them explicitly.
We hardcoded all the values to enable the New Architecture, so there is no way to disable it.

This is a behavioral breaking change, though.

## Changelog:
[iOS][Removed] - Removed the opt-out from the New Architecture.

Reviewed By: cortinico

Differential Revision: D79090048

fbshipit-source-id: 9779bfedf50748d7adbef5f7ef038f469e30efc2