Introduce pre-hygiene to apply default labels
This will re-implement !342 (merged) and it's based on !348 (merged) so we can dry-run the schedules changed here.
The triggered dry-run schedule: https://gitlab.com/gitlab-org/quality/triage-ops/pipelines/95100941
Closes #360 (closed), #345 (closed)
Edited by Lin Jen-Shin