Pass before_script and script as-is preserving arrays

What does this MR do?

Pass before_script and script to runner as-is preserving the arrays, and this will allow a runner to support multi-line commands properly:

test:
  script:
    - |
      bin/command my-multiline-command \
        --key=value \
        --url=http://address.com

We store before_script and script in ci_builds.options, but we still maintain commands for compatibility with other parts of the system. These are parts that should be moved out of ci_builds anyway, so there's no harm of storing that now, it only leads to slightly bigger storage requirements.

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

not yet