Embed jni libs in vendor apks for treble-ized devices

JNI libs used by bundled APKs have been installed outside of the APK
(e.g. /system/lib and /vendor/lib) to save space because multiple APKs
may share the same set of JNI libs.

However, this causes problem for treble-ized devices where access to
/vendor/lib is prohibited for system processes including Java apps.

So, the JNI libs are embedded into the APK when the APK is installed to
/vendor partition and the device is fully treble-ized.

Bug: 37491282
Test: Move an APK and its JNI libraries to vendor partition by setting
LOCAL_PROPRIETARY_MODULE := true and build:
The jni lib does not exist under /system or /vendor. unzipping
the apk reveals the jni lib under ./lib/<abi> directory.

Merged-In: I8389761dfbd28d181869d79f0bf988a1e4df2fca
Change-Id: I8389761dfbd28d181869d79f0bf988a1e4df2fca
(cherry picked from commit 1cb8dea6)