Create integration merge requests

What does this MR do?

Create integration merge requests

This renames the ui:create_integration_branch job to ui:create_integration_merge_request. It now also creates a merge request for the branch it created.

Other changes include:

• The integration branch is pushed to the canonical gitlab-org/gitlab repository now instead of a fork. The original reason for the fork was that cloning and pushing to the canonical repository often timed out. Fortunately, using the REST API to pull/push to the canonical repository is fast, so we can move back to that approach.
• The new merge request is assigned to the assignees of the originating merge request.
• The new merge request has these labels applied to ensure good test coverage from the start:
  • pipeline::tier-3
  • pipeline:run-all-jest
  • pipeline:run-all-rspec
• The new merge request description has a checklist of what to look for.
• More information is logged, for instance, the output of the yarn install command, and details about REST API calls.
• The temporary directory creation logic was simplified.
• An api function was extracted to simplify REST API calls.
• A prettyJson function was added, which truncates very large strings in object values to avoid filling up the CI job log (e.g., the content property of the fetched yarn.lock file blob).
• If there is an existing open merge request for the integration branch, it does not create a new one, or update it. It will still push the changes to the branch, though, and the existing merge request will reflect that.

Post merge tasks

• Archive the no-longer-needed gitlab-org/frontend/gitlab-ui-integrations> project
• Delete the GITLAB_INTEGRATION_REST_TOKEN CI token

Screenshots or screen recordings

N/A

Integrations

Kind of N/A; see !5272 (comment 2847040970)

Does this MR meet the acceptance criteria?

This checklist encourages the authors, reviewers, and maintainers of merge requests (MRs) to confirm changes were analyzed for conformity with the project's guidelines, security and accessibility.

Toggle the acceptance checklist

Conformity

• The “What does this MR do?” section in the MR description is filled out, explaining the reasons for and scope of the proposed changes, per “Say why not just what”.
  • For example, if the MR is focused on usage guidelines, addressing accessibility challenges could be added in a separate MR.
• Relevant label(s) are applied to the MR.
• The MR is added to a milestone.
• Added the ~"component:*" label(s) if applicable.
• A changeset is added when this MR will do a patch, minor, or major update. More information can be found in doc/publishing-packages.md.

Components

• GitLab UI's contributing guidelines.
• If the MR changes a component's API, integration MR(s) have been opened (see integrations above).

Documentation

• If creating a new component page from scratch, it follows the page template structure.
• Content follows the Pajamas voice and tone guidelines, falling back on the GitLab Documentation Style Guide when needed.
• Related pages are cross-linked, where helpful. Component pages have related components and patterns defined in their Markdown front matter.
• If embedding a Figma file, it follows the Figma embed guide.
• Review requested from any GitLab designer or directly from a maintainer or trainee maintainer.
• Maintainer review follows the Pajamas UX maintainer review checklist.

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• Security reports checked/validated by a reviewer from the AppSec team

Accessibility

If this MR adds or modifies a component, take a few moments to review the following:

• All actions and functionality can be done with a keyboard.
• Links, buttons, and controls have a visible focus state.
• All content is presented in text or with a text equivalent. For example, alt text for SVG, or aria-label for icons that have meaning or perform actions.
• Changes in a component’s state are announced by a screen reader. For example, changing aria-expanded="false" to aria-expanded="true" when an accordion is expanded.
• Color combinations have sufficient contrast.