Trigger vulnerability resolution suggestion via a GraphQL mutation

As part of Enable Vulnerability Resolution in the Merge Re... (gitlab-org#14862 - closed), the scope of this issue is to create a new GraphQL mutation that can be triggered via the merge request vulnerability modal and initiate the vulnerability resolution process on the backend.

This mutation should respond with a GraphQL subscription so that the frontend can wait for the response from the backend.

This issue also includes adding the ability to send a final response to the subscription so that the frontend is able to perform the necessary actions. The final response should include both the full URL to the link to the newly created MR comment, as well as the comment ID.