Use severity labels instead of priority for cherry-picker
This replaces priority with severity labels because priorities are ambiguous.
Example of a MR gitlab!26811 (merged) that was not adhering to https://about.gitlab.com/handbook/engineering/releases/#gitlabcom-releases-2
- It was a P1, because it was a high priority for the team writing the MR
- It was not a bug, regression or availability fix
- It was a feature
By using severities, I hope to make this difference a bit clearer.
Edited by Marin Jankovski