Draft: Add test-health::* labels to existing issues

⚠ When to run this one-off migration ⚠

• It should be run only when 1.39.0 or above of this gem is used in gitlab-org/gitlab.

Context

• Follow-up of gitlab-org/ruby/gems/gitlab_quality-test_tooling!251 (merged)
• Closes #1602 (closed)

What does this MR do and why?

• Add test-health:failures to test health issues with labels failurenew
• Add test-health:pass-after-retry to test health issues with ~"flakiness::*" labels or with [test, failureflaky-test]
• Add test-health:failures to test health issues with labels ~"slowness::*" labels or with [test, ~"rspec::slow-test"]

Expected impact & dry-runs

https://gitlab.com/gitlab-org/quality/triage-ops/-/jobs/8051195407

• 24'846 /label ~"test-health:pass-after-retry"
• 2'836 /label ~"test-health:slow"
• 1'987 /label ~"test-health:failures"

That's going to be a problem.

Action items

• If adding environment variables for reactive processors, update config/triage-web.yaml and .gitlab/ci/triage-web.yml
• (If applicable) Add documentation to the handbook pages for Triage Operations =>
• (If applicable) Identify the affected groups and how to communicate to them:
  • /cc @person_or_group =>
  • Relevant Slack channels =>
  • Engineering week-in-review

Closes #1602 (closed)