Allow push to the own repo using CI_JOB_TOKEN API

Related to issue: #389060

First iteration MR: !152096 (merged)

What does this MR do and why?

The second iteration to introduce API for push_repository_for_job_token_allowed

1. Introduce a REST API to update ci_push_repository_for_job_token_allowed
2. Introduce a GraphQL mutation to update pushRepositoryForJobTokenAllowed
3. Add documentation around ci_push_repository_for_job_token_allowed
4. Update a documentation around ci_pipeline_variables_minimum_override_role

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.

How to set up and validate locally

1. REST API

curl --request PUT --header "PRIVATE-TOKEN: PAT_token" "http://gdk.test:3000/api/v4/projects/59"  --form "ci_push_repository_for_job_token_allowed=true"

2. GraphQL update mutation

mutation ProjectCiCdSettingsUpdate {
  projectCiCdSettingsUpdate(
    input:{
      fullPath: "test_repository/push_to_own_repo",
      pushRepositoryForJobTokenAllowed: true
    }
  )
  {
    errors
  }
}

3. GraphQL expose query:

query {
  project(fullPath: "test_repository/push_to_own_repo") {
    name,
    ciCdSettings {
      pushRepositoryForJobTokenAllowed
    },
  }
}

answer:

{
  "data": {
    "project": {
      "name": "push_to_own_repo",
      "ciCdSettings": {
        "pushRepositoryForJobTokenAllowed": false
      }
    }
  }
}