sepolicy: allow apps to execute libs embedded inside vendor apk

Currently, some jni libs in /vendor/lib are allowed to be executed
in java process by labelling them as same_process_hal_file. This is
wrong because those jni libs are not in fact same process HALs.

After b/37481404, those jni libs for vendor apks are embedded inside the
apk just like downloaded apks.

In order to make this possible, appdomain is allowed to execute
vendor_app_file. Note that allowing this is not a Treble violation because
vendor_app_file is Java and JNI code only. Native libraries in
/vendor/lib are still prevented from being loaded in apps except for
those are labeled as same_process_hal_file AND are loaded via the
'sphal' namespace.

Bug: 37481404
Test: Phone application does not crash.
Change-Id: Ifaece2f05d0b20e28c4b1c0847f5ea0bb28ade02