Add start to widget app name layout gravity

This fixes the alignment issue in RTL. Seems like the default is start
if layout_gravity isn't set, but if you set layout_gravity to
center_vertical, you need to explicitly set start or it will go to the
left.

Bug: 188147009
Test: validated locally and in AS layout preview
Change-Id: Ic4b4d7e6dfe03e1e6dd3ead5c3821e77261b4bb5