Make perf metrics collection & output via instrumentation simpler

- Added includeDetailedStats metadata to TimedTest for collecting additional
  metrics like memory usage and binder transactions
- Added PerformanceCollectorTestCase interface for hard-typing test class as
  performance test while still able to inherit from instrumenation test classes
- Reverted previous changes to PerformanceTestBase, will deprecate
  PerformanceTestBase/Case in a future CL
- Removed 'performance.' prefix from keys written to instrumentation output