Automatically apply "SLO::Near miss" to S3 bugs nearing their SLO

What does this MR do and why?

What

Automatically apply SLONear Miss to severity3 typebug issues that are almost overdue, i.e. when 50% of the SLO has elapsed (source).

Why

This is similar to !3723 (merged) but for SLONear Miss labels.

This policy change has been been split off from the other MR, otherwise the 2 jobs would have started running concurrently against the same set of issues which are both SLOMissed and SLONear Miss. Which might have gotten messy/inaccurate, so it was best to merge the SLOMissed policy first (!3723 (merged)), let it run (which it did), and then merge the SLONear Miss policy (!3732 (merged)).

Dry run

https://gitlab.com/gitlab-org/quality/triage-ops/-/jobs/12078714312

121 issues impacted, which are indeed near miss S3 bugs (I spot checked a few manually).

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