API fuzz - configuration screen - Implement save

• Main issue: #299234 (closed)

Implement save.

• When clicking on the Generate code snippet button:
  • A GraphQL mutation is triggered to save the configuration and get the corresponding code snippet.
  • Open the code snippet modal.
• Code snippet modal:
  • Copy code snippet only copies the code to the clipboard.
  • Primary action copies the snippet to the clipboard and redirects to gitlab_ci_yaml_edit_url.
• Error handling.