Set TARGET_COPY_OUT_ for product/vendor in mainline

This product variable is used to generate the loader config (to use
either /system/product or /product), and the vendor one is likely
used in similar ways. Having these partitions is required for mainline
devices, so set it in the shared BoardConfig.

Bug: 80410283
Test: make
Change-Id: I6f2d94ff43572a28df54ea8c60f2d838a3b9216c