[services] Backup - Send attachments from pull backup reactor

Summary:
Depends on D4245

We want to send attachment holders for both logs and compactions.

The data is sent in the following order:

• compaction data
• compaction holders
• for log in logs
  • log data
  • log chunk

Test Plan: Services will still build properly. This change is eventually tested on the end of this stack when the logic for the backup test is added

Reviewers: palys-swm

Reviewed By: palys-swm

Subscribers: ashoat, palys-swm, Adrian, atul, yayabosh

Differential Revision: https://phab.comm.dev/D4246