Introduce PACKAGE_FIRST_ADDED broadcast

When an app first appears on a device, this new broadcast is issued
including to manifest receivers.  The more general PACKAGE_ADDED
broadcast continues to be issued for both first install and updates,
but is not delivered to manifest receivers of apps that target O+.

Bug 37219124
Test: manual

Change-Id: I59b0a0b0dce96a909076b41280771f63e59584be