Support scrolling of Updates tab.

This commit changes the Updates tab to use a ListView for its items. The
ListView has an extra header item that overlaps with the carousel tab
(if present), and implements the scrolling which hides part of the
carousel (excluding the tab itself).

The fragment now basically contains only a list view, which will store
all the items, and an optional title (I need to check if that's actually
needed, but for now it is there).

The extra header is implemented with a layout: for those configurations
where there is a carousel, the header contains a placeholder which is
the same size as the carousel; for those configurations where there is
no carousel, the header will be an empty FrameLayout (but in those same
cases, there is a header at the top of the list in the fragment's
layout).

This commit does not take care of making the scrolling work across the
two tabs, e.g., when switching between tabs. I will address those issues
in a follow-up.

Bug: 5119353
Change-Id: I0eb6dcc06d624991ab1f5f8fe1197337ba03286b