Backport PackageListObserver#onPackageChanged.

Added internally in Ic48e3c728387ecf02f89d517ba1fe785ab9c75fd,
of which this is a partial cherry-pick.

Bug: 137864893
Test: builds, boots
Change-Id: I6975e0b70ded6047e1ac8013a82bc35ff150f03b
Merged-In: Ic48e3c728387ecf02f89d517ba1fe785ab9c75fd
3 files changed