Add ecosystem stage-level RP triage issues

What does this MR do and why?

Monthly triage issues are generated for the Plan and Create teams to make it easier to add bugs and performance issues to the Release Post.

This change adds ~"devops::ecosystem" per gitlab-com/www-gitlab-com!97955 (comment 839795996)

The ecosystem team has one quirk in that ~"group::foundations" has no BE EM. However, this section should not appear anyway, as they won't have any BE issues to triage.

Expected impact & dry-runs

These are strongly recommended to assist reviewers and reduce the time to merge your change.

Action items

• (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