Add pipeline graph to editor page

What does this MR do?

Note ⚠ We are working behind FF: #270059 (closed).

This change adds the pipeline graph to the pipeline editor page in a separate tab.

Users are able to see their pipeline represented visually or as text.

Out of scope of this MR

• In this MR, we don't have a pipeline loaded yet, so we see no content.
• The appearance of the tabs does not match the file editor yet, but that will made possible by: gitlab-ui!1827 (merged)

Screenshots (strongly suggested)

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

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
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team

Related to #263141 (closed)