react-native-test-app-msal: Add ability to enable broker

What happened?

We need the ability to enable the broker: https://github.com/microsoft/rnx-kit/blob/ec46da029366f5ec15bdac0acdb9c06b407fad05/packages/react-native-test-app-msal/android/build.gradle#L136

In order to do that, we also need the ability to configure the keystore in react-native-test-app: https://github.com/microsoft/react-native-test-app/issues/691

Affected Package

react-native-test-app-msal

Version

trunk

Which platforms are you seeing this issue on?

• Android
• iOS
• macOS
• Windows

System Information

n/a

Steps to Reproduce

n/a

Code of Conduct

• I agree to follow this project's Code of Conduct