History WebUI: Move scrolling container out of inner components

This CL moves the scrollable container from out of <history-list>
and <history-clusters> to a parent, to prepare for content for
history embeddings that needs to be in the scrollable container
but outside of the child components. <history-list> and
<history-clusters> takes in a binding scrollTarget of the HTML
element that the parent uses as the scrollable container instead.

Bug: 329688583
Change-Id: I7e8018f18a55cda715364fbff52fef73821a76cb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5410709


Commit-Queue: John Lee <johntlee@chromium.org>
Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1281296}