Order apex files by destination path not source path

The destination path, i.e. the path the file will occupy in the APEX is
more stable and less likely to change than the source path, i.e. the
path of the file in the out or source directories. This makes it easier
to diff changes in the copy commands.

Bug: 179354495
Test: m com.android.art com.android.ipsec com.android.os.statsd com.android.conscrypt
      - verify that this does not change the contents of the apex files
      - verify that this does change the order of copy_commands for the above apexes
Change-Id: Ia9ebe8418c59903cd738ee0fb9262b3f32a4ddbf