Use RRO for product-specific framework resources

Currently framework-res is compiled and linked with the argument
'--product {PRODUCT_CHARACTERISTICS}' to select product-specific
resources. But that causes framework-res depend on the product
characteristics, making differences of system.img among targets.

Setting generate_product_characteristics_rro will automatically
generate an RRO package which contains resources having
product="{PRODUCT_CHARACTERISTICS}"'. The RRO package will be
installed to /product partition. framework-res will be compiled
with '--product default', making system.img identical to all
targets.

Bug: 294799593
Test: boot and idmap2 dump
Change-Id: I56d9f095aec01ba96aadb32ed9779a0b88f93103