Add odm and oem policies

This change adds parsing, encoding, and validating of odm and oem
overlayable policies to aapt2, libandroidfw, and idmap2.

Bug: 121033532
Test: aapt2_tests, idmap2_tests
Change-Id: Ifc0d4b6c9f9c37e06b2988abade69dbb277c50c2
27 files changed