(Bug 44072) Make modules target 'mobile'

Schema modules (and the core EventLogging module) Should target both
'desktop' and 'mobile'. Previously they were delegating to the value set
by the base class, which included only 'desktop'.

Adds a unit test to verify targets of schema modules.

Change-Id: Ieef3976848ef43a5e76081383c6a3f30c58071df