Use ro.product.vndk.version for unbundled product apks

Instead of using "ro.product.apps.unbundled", use
"ro.product.vndk.version" to determine if product apks are unbundled.
"ro.product.vndk.version" will be defined by
PRODUCT_PRODUCT_VNDK_VERSION. If it is defined, all product apks must
be unbundled.

Bug: 144534640
Bug: 127738095
Bug: 128557860
Test: boot and check logs if product apps are loaded successfully
Change-Id: I6d0f7c20e131dfe12203c63a14e6254a8223893b