Add retry pipeline command processor

What does this MR do and why?

Create a retry command as discussed in Only maintainer are allowed to retry jobs in Gi... (gitlab-org/quality/engineering-productivity/team#258 - closed)

Examples commands added by this MR:

• retry_pipeline 123 will retry all failed jobs in the pipeline with id 123
• retry_job 123 will retry a single job with id 123

This gives triagers an option to retry a pipeline or a job if they lack the permission to do so with their own account.

Next steps

We list these commands in the master broken incidents so triagers can see they are available. I will add this in a follow up MR.

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-policies-with-a-dry-run on how to perform dry-runs for new policies.

See https://gitlab.com/gitlab-org/quality/triage-ops/-/blob/master/doc/reactive/best_practices.md#use-the-sandbox-to-test-new-processors on how to make sure a new processor can be tested.

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