The admin setting updateautodeploy no longer exists. The two existing
config.php flags $CFG->disableupdateautodeploy and
$CFG->disableonclickaddoninstall merged into a single one.
Most of the functionality provided by this tool (typically the
validation and actual deployment of the plugin package) has been moved
to the core level. So this is becoming just a thin wrapper and user
interface for installing new plugins via the administration UI.
Also fixes MDL-49600 as we no longer keep the unzipped contents of the
packages in the persistent temp directories.
The script validate.php expects a ZIP file stored in a temporary
location. It extracts the ZIP (optionally renaming the root directory)
and executes the validator. Then it renders the validator log messages
and continue buttons.