[services] Backup - Add data hash to database manager

Summary:
Depends on D4412

linear task: https://linear.app/comm/issue/ENG-1288/properly-handle-the-dynamodb-item-size-limit

As we started to store the data hash in the log item in D4320, we also want to be able to store the in the database.

Test Plan: Services build

Reviewers: palys-swm, ashoat

Reviewed By: palys-swm, ashoat

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

Differential Revision: https://phab.comm.dev/D4322