Moves icon management to NotificationRowBinder.

This change moves the calls in NotificationEntryManager to
NotificationData.Entry.createIcons() and .removeIcons() to
NotificationRowBinder.inflateViews() to encapsulate all the view
handling in the latter class (and so that we can eventually not create
those icon views right away).

Test: atest SystemUITests, manually
Change-Id: Ie515c85b81ce6ad5de607b83e8f242d7ae03326e