Clean up how APK backups are made.

In preparation for supporting backup of APEX files.

Get the path to the apk using PackageInfo rather than through
PackageManagerInternal APIs. This new approach will work for both
APKs and APEX files.

Copy the apk manually rather than using PackageManagerServiceUtils,
which will work for both APKs and APEX files.

Bug: 112431924
Test: atest RollbackTest
Change-Id: Ifa9d42da9f0bf048f62dae891d59c3ac54fae438
2 files changed