Support multiple firebase app id/project id

## What feature would you like to see?
We would like firebase initial support multiple app-id/project , For example.
We have an project own by location A which use firebase push service which use firebase account A, now we wanna integrate firebase crashlytics and performance, but we must use account B own by location B. So we wanna when collect crash/performance use B , push with A .
I did some research , firebase have an API FirebaseOptions which is support initial multiple services account. So could you please implement this for crashlytics ?

https://github.com/firebase/snippets-android/blob/14cfefcaf00f9aae6f613281f46000d15f9047be/firebaseoptions/app/src/main/java/devrel/firebase/google/com/firebaseoptions/MainActivity.java

Describe the feature you would like to add, ideally proposing a specific API.

When we get a instance from https://github.com/firebase/firebase-android-sdk/blob/master/firebase-crashlytics/src/main/java/com/google/firebase/crashlytics/FirebaseCrashlytics.java
`
@NonNull public static FirebaseCrashlytics getInstance(String name) { final FirebaseApp app = FirebaseApp.getInstance(name); final FirebaseCrashlytics instance = app.get(FirebaseCrashlytics.class); if (instance == null) { throw new NullPointerException("FirebaseCrashlytics component is not present."); } return instance; }`

Pls refer to : https://github.com/firebase/firebase-android-sdk/blob/95b36fca16e4a4be231c435759db94ad4d3e8e61/firebase-common/src/main/java/com/google/firebase/FirebaseApp.java#L199

BTW ,depends lib as below

- com.google.firebase:firebase-common:20.0.0
- com.google.firebase:firebase-crashlytics-ndk:18.0.0

## How would you use it?

Suppose for collect crash/performance for our app.

Tell us how you'd use this feature in your app.