Normalize labels based on the internal mapping

We recently had an [issue](https://github.com/GoogleCloudPlatform/appengine-plugins-core/issues/911) that it was already triaged and assigned a label(testing), but still showed up in our un-triaged list. This is because `testing` is not considered a proper label in the [filter](go/cloud-java-rotations#github-issues-triage), we need to
normalize the labels based on the [internal mapping](https://g3doc.corp.google.com/devrel/cloud/infra/devrel_services/g3doc/user/github-tracker.md?cl=head#issue-type-mapping) so that the github labels are correctly recognized by buganizer.
We can start with adding labels like `type: process`, `type:question` etc.