Group community-related processors under processor/community

What does this MR do and why?

This groups community-related processors under processor/community for clarity of organization and ownership.

This also improves naming consistency of the processors and group them in triage/handler.rb as well.

Expected impact & dry-runs

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

See https://gitlab.com/gitlab-org/quality/triage-ops/-/tree/master/doc/scheduled#testing-with-a-dry-run on how to perform dry-runs.

Action items

• Update references in https://about.gitlab.com/handbook/engineering/quality/contributor-success/#automations-owned-by-the-team
• (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 #996 (closed).