Draft: Save pipelines on error

What does this MR do and why?

There are a number of ways to kick off a pipeline and some of them are failing silently.

This MR addresses this by introducing a feature flag which ensures failed pipelines are still created through all mechanisms which do not provide immediate user feedback of failures.

How to set up and validate locally

1. Create a repository with an invalid .gitlab-ci.yml
2. Note a pipeline is created and shows the error
3. Create a scheduled pipeline and either allow it to be executed automatically, or start it manually from the pipelines schedule page
4. Note the success message which appears in the UI, but then navigate to the pipelines and note that no pipeline was created

Now do enable the feature flag save_pipeline_on_error and do the same, you should see the failed pipeline created AND if you have it configured, you will receive an e-mail notification

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.