Extract native code from split APKs.

In the new split APK world, multiple APKs work together to define a
single package.  This means that native code may be split among those
APKs.  To handle this, extend NativeLibraryHelper to examine all
APKs in a package ordered by splitName.

A package has valid native code as long as one matching ABI is found
inside.  The "best" ABI found across all APKs is picked for the
entire package.  No attempt is made to ensure that every native
library defined is available for the picked ABI; that's the
responsibility of the installer.

Re-introduce PackageLite to represent a lightweight parsing of an
entire package, which may be a single monolithic APK or a cluster
of one or more APKs.

Remove native code extraction from InstallerSession, since it'll be
handled inside PMS for this release.

Bug: 14975160
Change-Id: I4f4db0f82e88a46101c7777499ebc0a11fd911f9