Merge changes from topics "remove_bootimage_sysprops", "sysprop"

* changes:
  Drop the dependency from vendor/build.prop to system/build.prop
  Remove ro.bootimage.* sysprops
  ro.build.expect.* sysprops are created in a separate rule
  Make use of ADDITIONAL_ODM_PROPERTIES
  Refactor post_process_props.py
  remove code for default.prop
  Make more use of ADDITIONAL_VENDOR_PROPERTIES
  ADDITIONAL_*_PROPERTIES are props determined by the build system