Switch PackageStatusStorage to XML-based storage

Based on feedback from a framework developer: an XML file can be used
instead of a Sqlite DB.

To run tests:
make -j30 FrameworksServicesTests
adb install -r -g
"out/target/product/angler/data/app/FrameworksServicesTests/FrameworksServicesTests.apk"
adb shell am instrument -e package com.android.server.timezone -w
com.android.frameworks.servicestests \
    "com.android.frameworks.servicestests/android.support.test.runner.AndroidJUnitRunner"

Test: See above.
Bug: 31008728
Change-Id: I1e6614d26df0e37ccea4dff82867e0b6aba39ca6