Add build_prop soong module

build_prop is a soong module generating {partition}/build.prop. It's
ported from build/make/core/sysprop.mk and will replace sysprop.mk in
the future. Currently used only by Android.bp cuttlefish system image.

Bug: 322090587
Bug: 346214958
Test: compare system/build.prop and aosp_cf_x86_64_system-build.prop for
      eng / user / userdebug
Change-Id: Iadb793a049b7be15b36f948c3a473105db3835a1