Fix overlapping text in NotificationHistoryActivity

Align the TextViews to end at the start at the expand button.
Make the label TextView single line and ellipsize it at the end.
Remove the RelativeLayout and flatten the view hierarchy.
Update background to fix the corners of the ripple effect.
Remove unused drawable xml.

Test: manual (a custom app with a long app name sends a notification)

Fixes: 239066636
Change-Id: I07c82c382138309417e3394574811afb7423c1e7