[A11y metrics] Adds feature duration message for logged in sessions

Logs feature duration if feature was enabled during a logged in
session, either when the feature is disabled or when the session
ends (due to profile change, pref disabled, or ash shutdown)

Bug: b:331856575
AX-Relnotes: N/A
Test: Manual, automated
Change-Id: I92e6f2f1513d1f42ff905ecf63cbfaf7db879022
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5425386
Reviewed-by: Anastasia Helfinstein <anastasi@google.com>
Reviewed-by: Evan Liu <evliu@google.com>
Commit-Queue: Katie Dektar <katie@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1283335}