Actor: Improve logging in ObservationDelayController

Improve logging by using async entries for state changes. However, this
requires omitting the page stability state since that's already covered
by async entries in PageStabilityMonitor itself (from
https://crrev.com/c/6997689).

Logs various events throughout the controller but now directly uses an
AggregatedJournal ref to avoid lifetime issues with the async entries.
This requires passing in the journal to the constructor.

Bug: b:434268231
Change-Id: Ib34f9f651ecd2337ff3729644b0b20a03f90fb8e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6996018
Commit-Queue: David Bokan <bokan@chromium.org>
Reviewed-by: Nan Lin <linnan@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1523289}