FcmRegistration: lazily initialize Firebase objects am: a8683c33e6 am: 8e0a40638d am: 2e031b271d

Original change: https://android-review.googlesource.com/c/platform/packages/apps/ImsServiceEntitlement/+/2021376

Change-Id: I2ae3048fcba479466b03bc40db542322c8f13ed3
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>