Mark stable and document ddmc apis

This CL also moves out utility methods to framework and removes them
from CorePlatformApi set.

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
 * Made DdmServer and DdmVmInternal final

Bug: 184654804
Bug: 154796679
Test: m update-api
Merged-In: Ia41e428fa3fe7129e0101b2aa29536682376c713
Change-Id: Ia41e428fa3fe7129e0101b2aa29536682376c713
6 files changed