doc: Update developer notes

Summary:
This is a partial backport of core#21202 and concludes backport of core#24931
https://github.com/bitcoin/bitcoin/pull/24931/commits/ce893c0497fc9b8ab9752153dfcc77c9f427545e

The code change from core#21202 was done independently by us in D4581

Depends on D14894

Test Plan: proof-reading

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D14895