Add default labeling policy to Delivery and Scalability issue trackers

Adding new policies for Delivery and Scalability issue trackers. At minimum we need to have team:: scoped labels applied to issues because number of issue boards depend on existence of this label and when creating an issue this is easy to forget.

The changes in this MR add the following:

• For https://gitlab.com/gitlab-com/gl-infra/delivery/issues, adds teamDelivery label by default
• For https://gitlab.com/gitlab-com/gl-infra/scalability/issues, adds ~"team::Scalability" label by default
• Changes the deprecated --project-id flag used by gitlab-triage to new --source-id flag. By default --source flag is set to project so I omitted it.