Merge READWRITEMANY into READWRITE
Summary: Backported commit 1/2 (2761bca997) from PR12683
Test Plan: make check
Reviewers: #bitcoin_abc, deadalnix, Fabien, nakihito
Reviewed By: #bitcoin_abc, Fabien
Maniphest Tasks: T634
Differential Revision: https://reviews.bitcoinabc.org/D2930