Allow non-references to be copied between AssetManagers

Hard-coded values in styles can be copied between AssetManagers even if
the source package is not present in the destination AssetManager. Only
references and strings should be prevented from being copied over
because they would be invalid in the destination AssetManager.

Bug:126400561
Test: manual
Change-Id: I970a3e961763b2c003c15b950d864a9a0b615022