Add auto cancel pipeline on job failure syntax support

What does this MR do and why?

This is the first step of #23605 (closed).

1. <-- HERE -->
2. Cancel a pipeline when configured to auto cance... (!141812 - merged)
3. Added documentation for workflow:auto_cancel:on... (!145709 - merged)

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This MR introduces the database models and .gitlab-ci.yml syntax for supporting the newly introduced workflow:auto_cancel:on_job_failure feature 🙂

I am also introducing a new feature flag, :auto_cancel_pipeline_on_job_failure, that can be used to enable or disable this new feature 🙂

Screenshots or screen recordings

N.A.

How to set up and validate locally

1. Make sure that pipelines with the following workflow syntax do not show any "syntax error"

   workflow:
     auto_cancel:
       on_job_failure: all|none

N.B.: this (the syntax support) is not behind a feature flag, only the memorization inside the database is.

MR acceptance checklist

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