Protected runner executes jobs on protected branch [Solution 1]

What does this MR do?

This MR is continued from https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/13192. To accomplish this feature, we need to implement a mechanism for "Protected runner executes jobs on protected branch. Unprotected runner executes jobs on unprotected branch". However, there is a technical challenge that ci_builds doesn't have data whether the ref is protected or not.

This MR addresses the challenge with Solution 1.

Solution 1. Persists protected(ref) flag on ci_pipelines table. builds_for_shared_runner and builds_for_specific_runner read the flag instead of executing protected_for? one by one.

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/13192#note_36332863

Update Aug 21st

We expand ci_biulds instead of ci_pipelines. See https://gitlab.com/gitlab-org/gitlab-ce/issues/33281#note_37674757.

Compared with solution2

• Pro

• Fast

• Scalable

• Con

• If user changes the ref protection, do we need to update the corresponded data on ci_pipelines? https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/13192#note_36334215

• Alter column on ci_pipelines

Are there points in the code the reviewer needs to double check?

How should we mark the protected flag on ci_biulds? Do we leverage it by only protected-branch-or-not?

Why was this MR needed?

This is aimed for %10.0

Screenshots (if relevant)

Edit Show When there is a only protected runnners and a job was created on a unprotected branch

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
• Review
  • [-] Has been reviewed by UX
  • [-] Has been reviewed by Frontend
  • Has been reviewed by Backend
  • [-] Has been reviewed by Database
• 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?

• https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/13192
• Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/33281
• Solution 2 => https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/13216

/cc @ayufan @godfat