Record MediaPreviews.UI.{Location}.{Type}.Duration metric

Records the length of time the preview is on-screen. As a simplification,
we will just record the length of time where {Location} is open.
{Location}: Permissions, PageInfo
{Type}: Camera, Mic, CameraAndMic
Value: Amount of time the preview is onscreen in seconds

Bug: b:329311590
Change-Id: I774f55e0731fb8b3e2ab9ef0a59b24377829948f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5379350


Reviewed-by: Bryant Chandler <bryantchandler@chromium.org>
Commit-Queue: Ahmed Moussa <ahmedmoussa@google.com>
Cr-Commit-Position: refs/heads/main@{#1277224}