Consider using owners or code-owners plugin instead of reviewers to auto-suggest reviewers for changes

As a result of QTQAINFRA-169 we have the reviewers plugin installed in gerrit.

It allows setting default reviewers based on filters per project, as can be seen in this change
https://codereview.qt-project.org/c/qt/qtbase/+/619839

But the filters and reviewers are stored in gerrit's meta/config branch. Also to create a change there, you need to be a Gerrit admin, or ask one to create a change.
This limits the visibility, usability and know-how of how to add/remove reviewers to repos or certain parts of the repo.

TLDR: Hard to do, nobody will do it unless they really put in the effort.

Having the reviewers in files inside the git repo itself is much more visible and accessible, anyone can propose changes to the reviewer via simply editing the file and pushing a change to gerrit, no special permissions necessary.

This was mentioned in QTQAINFRA-6939 and mentioned in some comments of QTQAINFRA-169.

That can be achieved using either the code-owners and owners plugins, and keeping OWNERS files in subdirectories of repos.

https://gerrit.googlesource.com/plugins/code-owners/ Developed and maintained by Google
https://gerrit.googlesource.com/plugins/owners/ Developed by GerrtitForge and maintained by community

The differences (biased) are showcased in video format starting at https://youtu.be/NfIHnJF30Wo?si=4paUKULuGDERlz1z&t=1266

code-owners doesn't support gerrit groups, owners does
code-owners uses free-form-ish text format for listing reviewers, owners uses yaml
code-owners offers a "suggest owners" button to add reviewers, owners automatically adds owners, and offers second plugin to auto-add reviewrs

So probably owners is better.

Piggy backing on this, we can in the future also codify the maintainer list like this, if the project agrees.