[comm-lib][blob-client] Extract error handling logic

Summary:
Noticed that response handling is repetitive. Ectracted a common utility function, and refactored some of these functions to use it and return early when possible.

Depends on D13644

Test Plan: cargo build -p comm-lib

Reviewers: varun, will, kamil

Reviewed By: kamil

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D13645