metrics: extract label definition and validation
What does this MR do and why?
In preparation for gitlab-com/gl-infra/delivery#2690 (closed) this merge request refactors our label implementation in delivery-metrics introducing the concept of a regexp based metrics.
This MR should be easier to review commit by commit.
- extract label definition and validation into its own package
- introduce a regexp based label
- provide a ready-made GitLab minor version label to apply for release pressure metrics
Related to: gitlab-com/gl-infra/delivery#2690 (closed)
Edited by Alessio Caiazza