[FR] Firebase Storage Emulator Support

As per https://firebase.google.com/docs/emulator-suite/install_and_configure#admin_sdk_availability the current version of the Firebase Admin SDK for Java does not yet provide support for Firebase Storage Emulator.

Indeed, even after setting `FIREBASE_STORAGE_EMULATOR_HOST` in my environment as per https://firebase.google.com/docs/emulator-suite/connect_storage#admin_sdks, that endpoint is simply ignored and requests are still sent to the usual remote URL(https://storage.googleapis.com/storage/v1...)

Is there a rough time horizon, in which this feature will be implemented?

Start with the Firebase documentation links in the issue, especially the Admin SDK availability and Storage Emulator connection sections, then trace how the Java Admin SDK selects the Storage request endpoint. There are no repository files or tests named in the report; done means FIREBASE_STORAGE_EMULATOR_HOST routes Storage requests to the emulator instead of storage.googleapis.com, with coverage for that behavior.

索引モデルが issue の本文から書いたものです。