Restrict vendor modules to help AOSP product distribution.

Bug: 5692177

If you set "PRODUCT_RESTRICT_VENDOR_FILES := true" in a product
configuration, this changes restricts that:
- No overlays in the vendor tree.
- No PRODUCT_COPY_FILES coming from the vendor tree.
- Any referenced package with Android.mk in the vendor tree must have
  LOCAL_MODULE_OWNER set to a value that's compared against a whitelist
  stored in the core build system.

Change-Id: I172b84c7c853e9a04bf9879ea8dec90bd5054230