Add support for auto-generated characteristics RRO

Setting Generate_product_characteristics_rro will automatically generate
an RRO package which contains resources with
'product="{PRODUCT_CHARACTERISTICS}"'. The RRO package will be installed
to /product partition. The app will be compiled with '--product
default', making the app identical to all targets.

Motivation for this change is to minimize divergence of system.img.

Bug: 294799593
Test: boot and idmap2 dump
Change-Id: I1371f7410a1ecf337e1f73214b024af39aa6d57a