Build super.img from images in target_files

For non-retrofit (launch) devices, super.img is used for factory, so
source images should be from target_files.

In this change, build-superimage-target procedure is converted to a
more flexible script so that it can be built.

Bug: 119322123
Test: build target files for device launch with dynamic partitions
Change-Id: I6ee0cc3e145357dfc74be248f81f5f8f4e51fc5c