Add new run keyword under job

What does this MR do and why?

This MR adds support for job-level run keyword.

We store the run config in BuildExecutionConfig and pass on to the runner in job response.

More details about the keyword and motivation - #440487

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

NA

How to set up and validate locally

1. Setup runner locally using docker by following runner setup.
2. Copy sample step config from the comment
3. The job should run successfully without any issues.
4. Check Ci::BuildExecutionConfig store the run_steps and associate it with the build and the pipeline you just ran.

Related to #440487