Add update FCM token grpc

Add update FCM API to the check in grpc definition and to
DeviceCheckInClient. The API will be used in future CLs

Bug: 367447984
Flag: EXEMPT low-risk refactor
Test: atest DeviceCheckInClientImplTest
Change-Id: If35daf24e929e5e06f252a4fa2b8475e2bf10547
7 files changed