Allow Instant Apps to read Settings defined by apps

This is a temporary solution, in the future we will investigate adding
an API that requires the app adding a setting to specify if the setting
should be visible to Instant Apps or not.

Test: run instant app from b/37765840, see denials are gone.
Bug: 37765840
Change-Id: Ib256d375d2a07f743b360c61ed25c9857aafa36c