Resolve "Run pipeline button for "Pipelines for merge requests""

What does this MR do?

Frontend:

(Note for the reviewer/maintainer, this code still uses the old non-vuex pattern with the eventHub)

• Renders the Run Pipeline button in the MR page only and only when the latest pipeline is detached
• Disables the button & shows a loading icon when the request is being made
• Updates the table once the post request has finished
• Handles the error
• Added specs

mobile	desktop	loading	error

Backend:

WIP

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry for user-facing changes, or community contribution. Check the link for other scenarios.
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Performance 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

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

Closes #65940 (closed)