Use AlphaSafeImageButton subclass - DO NOT MERGE

Bug: 27715789

On some platforms animating a View's alpha with a RippleDrawable
background can cause graphical artifacts. To combat this we provide a
lightweight ImageButton subclass which returns false for
View#hasOverlappingRendering() if it has a RippleDrawable for a
background. Fixed in v24.0.0 version of appcompat support lib.

Change-Id: I1baf16c11e9adfe6cbbd4b080aa7fa93915d888f