Write fingerprint to package map.

Write fingerprint to package.map fingerprint field. This involves some
re-work of how the fingerprint is calculated. Guard the write with a
new arg in create-storage, enable-fingerprint. The default value for
enable-fingerprint is false, and I haven't updated the build code to
pass in anything, so none of this code should run right now. Next step
is to create a build flag and use that to set enable-fingerprint so we
can roll out this change. Then, I will use the fingerprint in codegen as
well.

Bug: 316357686
Test: atest
Change-Id: Ie3a290864d4f971a3f1d070edb4dcefec36f05b6