Migrate Libraries/Text, Libraries/Share and Libraries/Settings to use export syntax (#48901)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/48901

## Motivation
Modernising the react-native codebase to allow for ingestion by modern Flow tooling.

## This diff
- Updates files in `Libraries/Text`, `Libraries/Share` and `Libraries/Settings` to use `export` syntax.
- Appends `.default` to requires of the changed files.
- Updates test files.
- Updates the public API snapshot *(intented breaking change)*

Changelog:
[General][Breaking] - Files inside `Libraries/Text`, `Libraries/Share` and `Libraries/Settings` use `export` syntax, which requires the addition of `.default` when imported with the CJS `require` syntax.

Reviewed By: huntie

Differential Revision: D68562844

fbshipit-source-id: bd71a341e33d3629121aa61549139c4b1cd62c3f