There are various composer components / dependencies that have been updated to be php74 aware.

Note that, explicitly, this doesn't cover MDL-67317 (behat own php74 compatibility problems) that will be handled apart.

So, it's time to produce new / updated composer.lock versions, both for 38_STABLE and master. Following the steps detailed @ https://docs.moodle.org/dev/Composer

That will lower the number of phpunit / behat failures (not fixing everything at all), ensuring we are running the latest packages. And, of course, keeping php71, php72 and php73 passing ok.

Final note, another update may be needed later (once we raise 3.9 requirements to be php72, or if any other component has more php74 compatibility fixes to incorporate). But that will be decided in the future.