Generate system diff between KATI and SOONG

There is an effort to generate system image with Soong, but there are
some difference in installed files between Soong defined system image
and KATI defined one. This change generates diffs between installed
files from two sources.

Bug: 346873717
Test: USE_SOONG_DEFINED_SYSTEM_IMAGE=true m -j on aosp_cf_x86_64
generated diff file.

Change-Id: I25c71f88d16a4efb873c21abe70ca9c41c6423ca
Merged-In: I25c71f88d16a4efb873c21abe70ca9c41c6423ca