Add MATCH_APEX flag to getInstalledPackages.

If set, PackageManager will query apexservice and ask for activated
packages.

Test: wrote a small app to test the new query.
Bug: 117589375
Merged-In: I498bd97896f3eab65c88e9684874a30713be585e
Change-Id: I498bd97896f3eab65c88e9684874a30713be585e
4 files changed