Increase maximum job retries to 20

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What does this MR do and why?

Increases the maximum job retry count to 20. This is useful for jobs expected to fail more than 3 times. It is also useful for enabling jobs to run on the "spot nodes" of various cloud providers (AWS, Azure). It may be cost effective to run a job on a spot node, but only if the job can retry enough times to get past a failure due to the cloud provider reclaiming the instance.

e.g. AWS spot nodes are 10% the cost of regular nodes. Therefore, a job can be retried 10 times on a spot node before it becomes more cost effective to run it on a regular node.

References

Closes #367916

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Register and create a gitlab runner
2. Modify the .gitlab-ci.yml of a repo (GitLab Test in the web IDE will work) to create a job that retries

stages:
  - first
job:
  stage: first
  script:
    - exit 1
  retry:
    max: 20

3. Commit the changes. A pipeline is created by the commit. It creates a job that is retried 20 times (21 runs). The job is designed to fail every run.
4. Update the job to retry a maximum of 21 times and commit. The pipeline will fail to create.

MR acceptance checklist

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