Only show recent items in the new section.

This commit limits the set of items in the new section to items that
have been receiving within the last 7 days.

In order to make the unread items more visible even when they are not in
the new section, use highlighting on them, both in the text and the play
icon.

Bug: 5403047
Change-Id: I577c58bfcb9ef2031839092d50f41c357c7decba