Add unittests for "ambiguous" content providers

Add CTS tests describing the behavior of "ambiguous" content providers.
These are content providers where the provider doesn't specify an
android:exported line.

For API versions 16 and below, the default value of android:exported
is "true". Add "PermissionDeclareAppCompat", with target API level
16, and verify that it's content providers are visible.

Update the current tests, and verify that content providers which
don't have an "android:exported" line are not exported.

Bug: 3306452

Change-Id: Id7e8b0721bbc53d8e610a053c3f545fabd4ae596
8 files changed