Rewrite aosp_crosshatch_car.mk to inherit aosp_product.mk

Let aosp_crosshatch_car.mk follow the CSI mainline convention.
AOSP crosshatch_car makefile now inherit mainline_system.mk
for system image and aosp_product.mk for product image.

Bug: 136525499
Test: Compare contents of $ANDROID_PRODUCT_OUT
Change-Id: I113a287cbb5346897fe214d2a64b5fa8a3b8d3ef