Expose NativeComponentRegistry API as JavaScript root export (#52999)

Summary:
Resolves https://github.com/react-native-community/discussions-and-proposals/discussions/893#discussioncomment-13449739

Expose NativeComponentRegistry as a root export on index.js.

## Changelog:

[General][Added] - Expose NativeComponentRegistry API as JavaScript root export

Pull Request resolved: https://github.com/facebook/react-native/pull/52999

Test Plan: Can import NativeComponentRegistry from root exort

Reviewed By: cortinico, cipolleschi

Differential Revision: D79721243

Pulled By: huntie

fbshipit-source-id: 77d94fb22255de020009ffe0e54d5030213519e2