Integrating simpleperf to app launch tests

1. This change is backward compatible. The old test command should still be
valid and should just run fine.
2. To test the path, use the original "am instriment" command and add -e
dispatcher com.android.performanceLaunch.DispatchActivity".

Bug: 28964480

Change-Id: Ib63581ee57c56f31264b12c8e7a5a21c2d621020