Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/41698

With the previous changes on the Pod configuration, the build setup for the New and Old architecture are the same.
The only observable difference happens at runtime.

This change:
1. Removes the build job that are split by architecture (which is now duplicated work)
2. Add two more test jobs to run runtime tests (unit and integration test) to make sure that the two architectures continue working.

## Changelog:
[Internal] - [CI] Remove duplicated build jobs, add tests jobs

Reviewed By: cortinico

Differential Revision: D51659275

fbshipit-source-id: 769c9ee004e7f4f1a7444f39c02b7083e007b780