ActivityManagerService: Add support for new stack dumping scheme.

Tombstoned now fully supports java traces and intercepts, and the
debuggerd dump API has been extended to support dumps of java traces.

This change switches ANR dumping over to using this API when the
right system property is set. The new flow is as follows :

- The system_server creates a new file using File.createTempFile for
  each ANR detected by the activity manager. All dumps associated
  with that ANR go into that file.

- All dumps are initiated using debuggerd client API (debuggerd_trigger_dump)
  which handles all the timeout measurement for us. It can also
  guarantee that no writes are made to the file after the method
  returns, so we have no need of inotify watches and other fiddly
  mechanisms to monitor progress. Also, this would give us the ability
  to add meta-information about timeouts etc. to the dump file itself,
  thougt that hasn't been implemented just yet.

Test: Manual
Bug: 32064548

Change-Id: I37e72c467e6dc29da4347c2a2829eeeeb1ad3490