[PEPC]: Observe intersection state of PermissionElement

This CL will disable the element when it's not entirely visible in the
viewport. It will also disable it momentarily when transitioning from
invisible to visible. The visibility state is observed and set using the
IntersectionObserver.

Bug: 1462930

Change-Id: I94cf3813eb0779ec46a409b6ed89cfa7fa1ea5c2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5310059


Reviewed-by: Mason Freed <masonf@chromium.org>
Commit-Queue: Thomas Nguyen <tungnh@chromium.org>
Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Reviewed-by: Stefan Zager <szager@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1270118}