Improve CombinedMessageQueue#mUseConcurrent logic

Check if process name contains "test". :/
Remove instrumentation check as it observes mutable state.
Now that we only look at effectively-immutable process state,
cache process-level checks.

Change-Id: Ia6b8a9f98d0e8e4eda2e240f3dbcdf5735cd754b
Flag: build.RELEASE_PACKAGE_MESSAGEQUEUE_IMPLEMENTATION