[identity] Pass Blob client to AuthenticatedService

Summary:
Added a BlobServiceClient member to the AuthenticatedService gRPC service. It's going to be needed to remove holders in the next diff

Depends on D13650

Test Plan: cargo build -p identity

Reviewers: varun, will, kamil

Reviewed By: kamil

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D13651