simpleperf: add script to manage app profiling process.

app_profiler.py follows the instruction of profiling an
app in README.md. Users can just set the configuration,
and let app_profiler.py do environment setup, profiling
and data collection work.

Bug: http://b/32834638
Test: run app_profiler.py on android M, N, O.
Change-Id: I2e08790396b02df32320eaa27b75d49108f4856f
6 files changed