Cleanup TODOs leftover from PR14119 backporting
Summary:
Final cleanup after PR14119
https://github.com/bitcoin/bitcoin/pull/14119/files
Depends on D3922, D3923, and others already landed
Test Plan: test_runner.py --extended
Reviewers: #bitcoin_abc, deadalnix, Fabien
Reviewed By: #bitcoin_abc, Fabien
Subscribers: Fabien
Differential Revision: https://reviews.bitcoinabc.org/D3924