Move asynchronous API calls to synchronous to match Firebase web JS SDK API

[russellwheatley]

We're moving RNFB API to match Firebase web JS SDK API, some API are currently asynchronous when they should be synchronous to match Firebase web JS SDK API.

For example, Auth: https://firebase.google.com/docs/reference/js/auth.auth

languageCode and tenantId are synchronous getters/setters.

This is an issue to track this work, and to help developers find an alternative solution to the deprecated JS debugger which has an issue with synchronous native calls.

@mikehardy - for visibility.

[mikehardy]

examples of how to make a native method synchronous, at least in old architecture ("Paper") react-native style (unsure if it is possible in Fabric / TurboModules)

Android:

• Add annotation argument to @ReactMethod call like so:
• https://github.com/react-native-device-info/react-native-device-info/blob/b5517cbc1362792abe4f44a27ca03029f5c40b73/android/src/main/java/com/learnium/RNDeviceInfo/RNDeviceModule.java#L320
• @ReactMethod(isBlockingSynchronousMethod = true)

iOS:

• Use different compiler preprocesser directive RCT_EXPORT_BLOCKING_SYNCHRONOUS_METHOD
• https://github.com/react-native-device-info/react-native-device-info/blob/b5517cbc1362792abe4f44a27ca03029f5c40b73/ios/RNDeviceInfo/RNDeviceInfo.m#L172C1-L172C39

Both of those break the ability to use the old react-native javascript debugging interface as that pulls the bundle across the network to the debugger, executes it in the debugger context and sends the results back and forth to the native app, something that can't happen synchronously.

Historically the answer to this is "use reactotron" for debugging, but I believe react-native now has wholly moved to "React Native DevTools" as official recommendation