Pipeline start_date not filled if all jobs filled.

Summary

It looks like if all the jobs in a pipeline are declared as delayed, started_at won't be filled properly.

Steps to reproduce

Create a project with all jobs declared as delayed. Call the pipeline api, started_at will be nil

Example Project

https://gitlab.com/alexandru.bumbacea/test-ci-delay https://gitlab.com/api/v4/projects/18366744/pipelines/139573345

What is the current bug behavior?

started_at field is not populated

What is the expected correct behavior?

started_at field is populated with time.now when the first job runs.

Possible fixes

https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/models/ci/pipeline.rb#L162