Add platform_apis property to APEX module type

The property is used to allow non-updatable APEXes to use platform APIs
(e.g. symbols marked as "# platform-only").

Bug: 191637950
Test: m com.android.virt com.android.compos
Merged-In: Id2410b4e38a78ec2146a42298840954381a7c472
Change-Id: Id2410b4e38a78ec2146a42298840954381a7c472
(cherry picked from commit fb63625a)