Allow Google Chat notifications to be filtered for specific pipeline sources

This feature proposal was created on behalf of a GitLab Ultimate customer (internal link) via a support ticket (internal link)

Proposal

Currently, with the Google Chat (hangouts) integration, it's possible to create a webhook for failed pipelines (Notify only broken pipelines). Currently, this includes any failed pipelines. It would be beneficial to be able to select specific pipeline sources (Scheduled, pipeline execution policy, scan execution policy, for some examples) to reduce noise and allow users to set up real-time monitoring for business critical pipelines.