A few fixes to AssetManager2 for compat

Theme copying should behave the way it did with the old AssetManager
(copy only the framework attributes when copying from a Theme object
from a different AssetManager).

Cleanup the dependencies on libziparchive in ApkAssets.

Test: make libandroidfw_tests
Test: out/host/<platform>/nativetests64/libandroidfw_tests/libandroidfw_tests --testdata=frameworks/base/libs/androidfw/tests/data
Change-Id: I973f7e6eb14ce311306e2ec66a623a4790c8d233