"Run manually" is a bit meh, as it runs the cron synchronously (so you
have to wait for it, and hope it doesn't run for longer than the
request timeout which may be smaller than the cron timeout) and it can
run in a subtly different environment than normal, which can lead to
different behaviour.
Instead add a button to enqueue a cron trigger, now that they exist
that's much closer to what we actually want, and it does run the cron
in a normal / expected environment.
