add release/debug switch script (#52498)

Summary:
Fixes #T228219721

This commit adds the debug/release switch script like we have for rn deps and hermes for react-core prebuilt:

- Added script: replace-rncore-version-js
- Inserted script into React-Core-prebuilt podspec
- Updated rncore.rb with correct filenames

bypass-github-export-checks

## Changelog:

[IOS] [ADDED] - add release/debug switch script for React-Core-prebuilt

Pull Request resolved: https://github.com/facebook/react-native/pull/52498

Test Plan: Run in RNTester and switch between release/debug

Reviewed By: rshest

Differential Revision: D78012917

Pulled By: cipolleschi

fbshipit-source-id: 71cad23cd41484a8253fc89d5dce8653649657a0