Add super_image module type and create super image module in fsgen

fsgen processes the variables exported from make and create
the super image module. This module generates the misc-info.txt,
which is used by build_super_image.py to build the super image.

Test: CI
Bug: 376726109
Change-Id: I74a3e68d697704f36a770b3c83e5f8821b3ac128