APEX carries required properties of its dependencies

When a module is included in an APEX and the module is not directly
installed to the system partition, the 'required' property of the module
is lost. The APEX containing the module now carries the property from
its dependencies.

Bug: 146549048
Test: m
Change-Id: Ie21cc7b8420c6126c855e66c2363644de4a7ef42