dexopt: Add listeners when packages are updated by bg-dexopt

The plan is to use it for iorap to purge its traces when a package
is updated.

Bug: 150640692
Test: adb shell cmd package bg-dexopt-job com.google.android.GoogleCamera
Change-Id: I45f4dacc1630c4afd7cf2321371a04f79ef18d9e