Add MessageLoopThread, ExecutionBarrier, and performance tests

* Add MessageLoopThread to abstract thread implementation to our code
* Add ExecutionBarrier utility class to help with thread synchronization
* Add more performance tests and performance benchmarks to evaluate
  execution efficiency in both batch and sequential usages, for various
  thread implementations including:
  - libosi reactor on pthread
  - MessageLoop on libosi reactor on pthread
  - MessageLoop on STL std::thread
  - MessageLoop on Posix pthread
  - MessageLoop on libchrome base::Thread
  - MessageLoop on MessageLoopThread

Bug: 110303473
Test: make, native and Java unit tests,
      test/run_benchmarks.sh net_benchmark_thread_performance,
      test/run_unit_tests.sh net_test_performance,
      test/run_unit_tests.sh bluetooth_test_common,
      testplans/details/184455/3975
Change-Id: I5b4ce2ee910a0f1d2edf95e0296916dea04d3f89