add vulkan anv support

anv implements Vulkan HAL without requiring additional wrapper/stub
anv is added as vulkan.android-x86 module to PRODUCT_PACKAGES
and PRODUCT_COPY_FILES is used to install android.hardware.vulkan.{level,version}.xml

ro.hardware.vulkan property is set by init.sh init_hal_vulkan() function
based on the drm fb kernel module inteldrmfb