Remove scanPackageInternal()

The final, major refactoring for this release. Replace
scanPackageInternal() with addForInit(). This new method delegates
all modifications of the package setting object to the existing
scanPackageOnly() method.

There is one block of code where we modify the ApplicationInfo
object in the PackageParser.Package. It could be argued [and I would
agree] that the ApplicationInfo doesn't belong in the Pacakge
object at all. But, regardless, updating this info is being done
in addForInit(). It would be ideal if we could push this down to
scanPackageOnly(). Unfortunately, we expect the ApplicationInfo
to be updated correctly prior to scanPackageOnly().

Bug: 63539144
Test: Manual.
Test: w/ base image
Test: 1] upgrade OTA
Test: 2] clean flash
Test: w/ image containing additional applications
Test: 1] add a system application
Test: 2] add a system application w/ version installed on /data. version on /data has greater version code
Test: 3] add a system application w/ version installed on /data. version on /data has lower version code
Test: 4] add a system application w/ version installed on /data. version on /data has signature mis-match
Test: 5] remove a system application
Test: 6] remove a system application w/ upgrade installed on /data
Test: 7] update a system application
Test: 8] update a system application w/ upgrade installed on /data. version on /data has greater version code
Test: 9] update a system application w/ upgrade installed on /data. version on /data has lower version code
Change-Id: I00a6f1cd056d9e5ee81154a522b7d50ea9174273