Summary:
This PR converts the HelloWorld app to Swift. The HelloWorld app is our internal copy of the Template and the template is now using Swift. It's important that this macroscopic changes are synched between the template and HelloWorld, otherwise we risk to ship changes that works in the helloworld app but that break the template, and therefore the next release. That already happened once this month.
## Changelog:
[Internal] - Migrate HelloWorld app to swift
Pull Request resolved: https://github.com/facebook/react-native/pull/48246
Test Plan: GHA
Reviewed By: cortinico
Differential Revision: D67143408
Pulled By: cipolleschi
fbshipit-source-id: f74412116570e44c2a394173f7d4d3b6dd85e2e5
