[lib] Introduce combined padding interface

Summary:
Part of ENG-3099

This diff is combining two previous diffs and finally allows to pad the data to multiples of 10KB (forty 250-byte blocks)

The whole idea is described in this Notion doc.

Depends on D7060

Test Plan: Added unit tests. Also tested using my CLI tool and hex editor / viewer (e.g. xxd tool). The CLI tool is also available in the Notion doc above

Reviewers: atul, marcin, tomek

Reviewed By: atul

Subscribers: anunay, ashoat, tomek

Differential Revision: https://phab.comm.dev/D7061