fw/b: Use ro.build.date to signal OTA upgrades

Squash of:

Author: dhacker29 <dhackerdvm@gmail.com>
Date:   Tue Nov 24 01:53:47 2015 -0500
    Core: Use ro.build.date to signal mIsUpgrade
    M: We use a static fingerprint that is only changed when a new OEM build is released, so
       every flash shows Android is starting instead of upgrading.  This will fix that.
    N: even though we dont have the dexopt sceen on N, this is still needed to delete the
       correct caches, and grant/deny specific runtime permissions like a true oem update
       would do.
       Updated for Nougat By: BeansTown106
    Change-Id: I0e3ed5c8f0351e48944432ae6a0c5194ddeff1fa

Author: Sam Mortimer <sam@mortimer.me.uk>
Date:   Fri Sep 28 13:45:00 2018 -0700
    fw/b UserManagerService: Use ro.build.date to signal upgrades
    *) We changed PackageManagerService to use Build.DATE instead of
       Build.FINGERPRINT to detect upgrade.  Do the same for
       UserManagerService.
    *) Affects generation of preboot intent and app data migration.
    Change-Id: I56887b7ca842afdcf3cf84b27b4c04667cf43307

Author: Wang Han <416810799@qq.com>
Date:   Sat Dec 29 23:33:20 2018 +0800
    ShortcutService: Use ro.build.date to signal package scanning
     * Affects system apps scanning.
    Change-Id: I5f6d6647929f5b5ae7e820b18e95bf5ed2ec8d1c

Change-Id: If0eb969ba509981f9209ffa37a949d9042ef4c2a