startop: Rewrite metrics parsing using python.

Shell version metrics parser generates some strange results when called
from Python.

Test: pytest logcat_utils_test.py
Test: pytest adb_utils_test.py
Test: pytest run_app_with_prefetch_test.py
Change-Id: I44a464f7e87f35ecc283c5108577eb33ad394fc6
6 files changed