Instead of hard-coding the logic for empty modules, just re-use the
{TriggerCallbacks} method. This will also ensure that the
{finished_events_} set will be populated correctly, such that callbacks
added later will still receive the events.

R=ahaas@chromium.org

Bug: chromium:1101340
Change-Id: I6641f23dc0459d0b6591bb03cc8c1b99dcaa90ff
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2351669Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69368}