Move dump-products back to the config stage

It's unnecessary to run all the make file parsing to dump product
configs. Move the dumping to product_config.mk instead, but switch
the output to $(warnings) as stdout is a bit sensitive during
the config stage.

Test: multiproduct_kati -only-config dump-products
Change-Id: I8c7365c9f90ea2bf152b82dfb983bfb0cdcb1697
diff --git a/core/product.mk b/core/product.mk
index 0baa9f2..b58898e 100644
--- a/core/product.mk
+++ b/core/product.mk
@@ -233,10 +233,10 @@
     PRODUCT_CHECK_ELF_FILES \
 
 define dump-product
-$(info ==== $(1) ====)\
+$(warning ==== $(1) ====)\
 $(foreach v,$(_product_var_list),\
-$(info PRODUCTS.$(1).$(v) := $(PRODUCTS.$(1).$(v))))\
-$(info --------)
+$(warning PRODUCTS.$(1).$(v) := $(PRODUCTS.$(1).$(v))))\
+$(warning --------)
 endef
 
 define dump-products