Record proto to file in am instrument

Add an option -f to record instrumentdata proto produced by am instrument
to a file in addition to printing to stdout. Default path is
/sdcard/instrument-logs/log-yyyyMMdd-hhmmss-SSS.instrumentation_data_proto.
If the file exits, it will be deleted before writing. Path can be changed
via optional <FILE> argument after -f.
If -f and -m are both present, proto will be written to a file and print
to stdout.

Test: build, flash and run:
bit -bi FrameworksCoreTests
adb shell am instrument -w -r -f tmp/tmp.log \
-e class com.android.internal.os.BatteryStatsNoteTest \
com.android.frameworks.coretests/android.support.test.runner.AndroidJUnitRunner

Change-Id: Iabc320c066d5995eee842c26416623eeb3d403f4