Mention the module's status in API review commit messages

It's a relevant detail that reviewers need to take into account; and the script should be able to extract this information from qt5/.gitmodules lines matching ^\s+status\s*=\s*(addon|deprecated|essential|ignore|preview)$. By default (since that's where it's checked out when generating API reviews) this will be the prior tag's status of the module; which kinda makes sense (if the module was in preview and we've changed the API on the way to putting it into a more restrictive status). It may also be worth reporting the new status, if different; the message about this can be a simple "This module has status $status." when unchanged, but needs to be something like "This module changed status from $oldstatus in $LAST to $newstatus in $NEXT." when it changes.