Reworked Activity Monitoring test

There are multiple problems with existing design:
  - activities sometimes run in separate process making semaphore
  synchronization useless
  - failing inside activities results in some other test crash (which
  is very misleading)
  - polling is just a bad pattern

Test: runtext -x packages/services/Car/tests/carservice_test

Change-Id: Ie3097c61764163f52e0bbd8c070e7085e21e0c9f
Fix: b/66448797, b/66955438
3 files changed