Add checker to support createUserContext().

To avoid an explosion of startActivityForUser style methods, we've
converged on recommending the use of Context.createContextAsUser(),
and then ensuring that all system services pass Context.getUserId()
for any int userId arguments across Binder interfaces.

This design allows developers to easily redirect all services
obtained from a specific Context to a different user with no
additional API surface.

Bug: 115654727, 159626156
Test: atest error_prone_android_framework_test
Change-Id: I2d665016e8356807c371a1e18a4e102dea5b5d8e