avb_storage: fix nonce update; enable clearing

Nonce updating was copying without the
incoming offset and was not using the VERSION_SIZE
constant. This changes fixes the storage as well as
adds a mechanism for resetting the nonce when not
in production mode (without a reinstall) and binds it into
the ese_boot_tool and the boot interface (making a
framework for factory rese without adding it explicitly).

Test: Used increasing nonces and made sure they were single use and only
newer ones worked by: set-carrier, set-production, unlock-last,
unlock-newer, unset-production, set-carrier, ...
Bug: none

Change-Id: I038229c1bb089b2d5f98faeed81714dfc1c32e36