change mechanism to report performance results

- For device side, use Instrumentation.sendStatus instead of exception
- Because of it, all tests need Instrumentation, and PtsAndroidTestCase is
  actually an ActivityInstrumentationTestCase with DummyActicity.
- In TF side, the result is passed as a test metrics.
- Host side tests uses static HashMap to store the result and retrieve it
  as the current stack does not have test metrics in host side.
- Key used is device_serial#class_name#method_name to make the storing unique to
  individual test case, and should be safe for concurrent runs

Change-Id: I254d72f2250d751f8e1e676e6dfe28837b4cd507