Add DifferenceFormatter

Summary:
This is a backport of Core PR18112 [3/5]
https://github.com/bitcoin/bitcoin/pull/18112/commits/10633398f2dddf929d3f535aa48d138ad5e6c50f

Depends on D8787

Test Plan: ninja

Reviewers: #bitcoin_abc, majcosta

Reviewed By: #bitcoin_abc, majcosta

Subscribers: majcosta

Differential Revision: https://reviews.bitcoinabc.org/D8788