Make priority and severity scoped labels

Per @tipyn in https://gitlab.slack.com/archives/C3JJET4Q6/p1568852155060400

We also have discussed making ~S1 ~S2 .. and ~P1 ~P2 labels scoped before. gitlab-org/gitlab#27906 (closed)

Right now as teams and groups are getting better at using these labels we should consider changing them to scoped labels so that only one of the labels are present when changing.

Priority

• ~P1 to priority1
• ~P2 to priority2
• ~P3 to priority3
• ~P4 to priority4

Severity

• ~S1 to severity1
• ~S2 to severity2
• ~S3 to severity3
• ~S4 to severity4

I believe the next steps are to estimate the work and changes need in all of our systems. Triage automation and charts to reflect this.

Steps:

0. gitlab-org/gitlab ➡ gitlab-org/gitlab!39136 (merged) and gitlab-org/gitlab!40280 (merged)
1. gitlab-org/release-tools ➡ gitlab-org/release-tools!1151 (merged)
2. gitlab-com/www-gitlab-com ➡ gitlab-com/www-gitlab-com!59662 (merged)
3. gitlab-org/quality/triage-ops ➡ !574 (merged)
4. gitlab-org/gitlab-insights ➡ gitlab-org/gitlab-insights!197 (merged)
5. gitlab-org/quality/insights-config ➡ insights-config!13 (merged)
6. gitlab-com/gl-infra/incident-management ➡ https://ops.gitlab.net/gitlab-com/gl-infra/incident-management/-/merge_requests/18
7. gitlab-com/gl-infra/triage-ops ➡ gitlab-com/gl-infra/triage-ops!43 (merged)
8. gitlab-com/gl-infra/production ➡ gitlab-com/gl-infra/production!34 (merged)
9. (merge around the time we rename) gitlab-org/quality/triage-serverless ➡ triage-serverless!29 (merged)
10. Rename the labels to scoped labels for gitlab-org https://gitlab.com/groups/gitlab-org/-/labels?search=P1
11. Rename the labels to scoped labels for gitlab-com https://gitlab.com/groups/gitlab-com/-/labels?search=P1
12. (after renamed) gitlab-org/release-tools ➡ gitlab-org/release-tools!1155 (merged)

@gl-quality/eng-prod