OMS: Assert which packages are updated

When the overlay manager is initialized and when packages are
installed, upgraded, or removed, the overlay manager must report any
updates to the currently enabled overlays for each package to PMS.

Test that when a package event happens, all packages that may have
their overlays affected are returned as updated packages from the
OMSImpl event methods.

Bug: 180016597
Test: atest
Change-Id: I9906f8805a2c2728e8c8b57ab9990b169ef06a2d