Build the React Native NPM package when git is not available (#34694)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/34694

TL;DR Relax the assumption of having git to build the RN NPM package.

We do have two CI Systems: CircleCI for OpenSource and Sandcastle for Internal. It's crucial that the two CIs are aligned.

We currently don't have a way to test the new app template on Sandcastle for Android & iOS.
This results in scenarios where internal Diffs gets landed and break the public CI externally.

This is preparation work to then be able to build the RN NPM package in Sandcastle (which will be done in a follow-up diff).

With this we also introduce the restoring of all the changed files after the publishing script is done.

## Changelog

[Internal] [Added] - Made it possible to create publishing NPM packages in Sandcastle.

Reviewed By: cortinico, cipolleschi

Differential Revision: D39467471

fbshipit-source-id: b0de88a768b8a2fb798dd684fa8f97f4d0acb751