Change the option to use scheduling instead of next_run_scheduled

What does this MR do and why?

This is a fix forward for !110716 (merged) to use scheduling option.

Because if next_run_scheduled is used, we will need to update all the other places and make sure they pass next_run_scheduled: true.

If we use scheduling, we only need to update only one place which is the PipelineScheduleWorker.

Screenshots or screen recordings

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How to set up and validate locally

1. Enable feature flag by running:

   rails runner 'Feature.enable(:ci_use_run_pipeline_schedule_worker)'

2. create a new project 338609-test-play-button
3. add CI config by going to CI/CD -> Editor with the following content:

   image: busybox:latest
   
   build:
     script:
       - echo "Do your build here"
       - sleep 15

4. go to CI/CD -> Schedules and create a schedule
5. click the Play button for the created schedule
6. go to CI/CD -> Pipelines and check if the pipeline for this schedule is created and runs
7. wait until the next schedule time and see if the pipeline is triggered as scheduled or run this command in Rails console to trigger it now:

   Ci::PipelineSchedule.find($ID_FOR_THE_CREATED_PIPELINE_SCHEDULE).update_columns(next_run_at: 1.day.ago)
   PipelineScheduleWorker.new.perform

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.

Related to #338609 (closed)