[services] Backup - Blob Get Client - Prepare for error handling

Summary:
Depends on D5074

Linear task: https://linear.app/comm/issue/ENG-1734/improve-error-handling-system-in-the-blob-client

Preparing for the upcoming changes in error handling. I'm going to be using anyhow, I saw we use it in the tunnelbroker as well.

Test Plan:

cd services/backup/blob_client
cargo check

after running localstack, blob, and backup (in this particular order), this still works:

yarn run-performance-tests backup

Reviewers: jon, ashoat, tomek, varun

Reviewed By: jon, ashoat, tomek

Subscribers: ashoat, tomek, atul, abosh

Differential Revision: https://phab.comm.dev/D5089