refactor: improve code readability of the RegionDiscovery file
refactor: improve code readability of the RegionDiscovery file

- improve code readability of the RegionDiscovery file
- add code comments in the RegionDiscovery file

AzureAD/microsoft-authentication-library-for-js,AzureAD/microsoft-authentication-library-for-js,AzureAD/microsoft-authentication-library-for-js,AzureAD/microsoft-authentication-library-for-js,AzureAD/microsoft-authentication-library-for-js,AzureAD/microsoft-authentication-library-for-js,AzureAD/microsoft-authentication-library-for-js,AzureAD/microsoft-authentication-library-for-js