apex: Restrict usage of "use_vendor"

When use_vendor is used, native modules are built with
__ANDROID_VNDK__ and __ANDROID_APEX__, which may cause
compatibility issues. (e.g. libbinder)

Even though libbinder restricts its availability via
'apex_available' property and relies on yet another macro
__ANDROID_APEX_<NAME>__, we restrict usage of "use_vendor:" from
other APEX modules to avoid similar problems.

Bug: 142684427
Test: m -j
Change-Id: Ibc781de2efcd20cb6688a183b08e908a8a6e2593