[lib] Convert update data into raw update info in a spec

Summary:
Move the code to specs.

Depends on D9745

https://linear.app/comm/issue/ENG-4233/introduce-update-specs-containing-functions-from-update-utils

Test Plan: Reintroduce the old code and check if it gives the same result.

Reviewers: kamil, inka, bartek

Reviewed By: kamil

Subscribers: ashoat, wyilio

Differential Revision: https://phab.comm.dev/D9746