Delayed install completion

This change is an attempt at delaying the install complete callback
to the installer on a DONT_KILL install until the package indicates
that it as completed updating its classpath with the new APKs.

Bug: 80269951
Bug: 109751013

Test: manual test of dynamic delivery/instant apps

Change-Id: I689ec523522da37987cff9b1a67eaae9e5633ffb