Fixing HUN translation in split shade and changing appearFraction to use...

Fixing HUN translation in split shade and changing appearFraction to use expansion fraction for non-HUN use cases

AppearFraction change is behind a flag enabled by default for teamfooding.
Also fixing translation of QS in split shade, which became very visible after changing appearFraction.

This doesn't make HUNs in split shade perfect yet, but works good enough for the case when there are at least two notifications in NSSL. Fix for when HUN is the only notification will come in future CL.

Test: get heads-up notification in split shade and swipe down or up
Test: testing notifications on handheld and making sure there are no visible changes
Test: NotificationStackScrollLayoutTest
Bug: 246353296
Bug: 232349737
Change-Id: Ieda32dd694e5f540510b46fe88f037dc7a2ff045