Refactor ddm ChunkHandler utility methods from libcore to framework

As a part of internal libcore cleanup three utility methods for ddm
chunks (de)serialization were removed from the CorePlatformApi set and
moved to framework.

As a part of API council review made following changes:
 * Renamed connected/disconnected callback methods to
   onConnected/onDisconnected, respectively
 * Made unregisterHandler method a part of core api
 * Renamed threadNotify/enableRecentAllocations setters

Bug: 154796679
Bug: 184654804
Test: m droid
Change-Id: I1d43f12aaf70c7c079577d3f3248248ed39f9865