Send BOOT_COMPLETED when updating system apps

Previously, when a system app was updated, it wasn't getting
BOOT_COMPLETED broadcast.
sendPackageAddedForUser was extended to support multiple userIds and also
send LOCKED_BOOT_COMPLETED. handlePackagePostInstall is now using the same
method as installExistingPackageAsUser

Test: pm install --user X -r systemAppV2.apk
Bug: 32242899
Change-Id: I75fe955aaf02d0a4c80b3604e3ef82316bf5dbc0