Firebase Auth Emulator interferes with Firebase Storage

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### [REQUIRED] Step 2: Describe your environment

* Operating System version: Windows 11
* Firebase SDK version: ____
* Library version: 9.1.1
* Firebase Product: auth, storage

### [REQUIRED] Step 3: Describe the problem

We access the Auth and Storage services in our project using this Java Admin SDK.
Recently, we wanted to make use of the Auth Emulator for development purposes. However, after enabling the emulator by setting the `FIREBASE_AUTH_EMULATOR_HOST` environment variable, the Storage calls stop working and return 401 Unauthorized.

It seems that by setting the `FIREBASE_AUTH_EMULATOR_HOST` environment variable, the [whole project enters an emulator mode](https://github.com/firebase/firebase-admin-java/blob/e8ec68c97929972acdbe05b79b5ea18f077a08a2/src/main/java/com/google/firebase/auth/internal/Utils.java#L27) and [uses emulator credentials](https://github.com/firebase/firebase-admin-java/blob/master/src/main/java/com/google/firebase/ImplFirebaseTrampolines.java#L47). The emulator credentials should be made to only apply to Auth calls.

Furthermore, I could not even find a way to create two instances of FirebaseApps (one with the emulator enabled and one disabled), since the check for `FIREBASE_AUTH_EMULATOR_HOST` is static and shared program-wide.

#### Steps to reproduce:

Use Auth and Storage in a production project. Enable `FIREBASE_AUTH_EMULATOR_HOST` and Storage stops working.

Start by reading src/main/java/com/google/firebase/auth/internal/Utils.java and src/main/java/com/google/firebase/ImplFirebaseTrampolines.java, especially the FIREBASE_AUTH_EMULATOR_HOST and emulator-credential handling. Reproduce the issue with Auth and Storage enabled together, then verify that Storage calls remain authorized while emulator credentials apply only to Auth; also check whether separate FirebaseApp instances can differ in emulator configuration.

Scritto dal modello di indicizzazione a partire dal testo della issue.