Add API Fuzzing report type to backend

What does this MR do?

Add a new report type api_fuzzing for the API Fuzzing security analyzer to the backend.

The new report type uses the same schema and parser as DAST. This simplifies the implementation.

Addresses #258203 (closed)

Screenshots

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

Manual testing:

1. Pipeline that submits an api_fuzzing report.
2. Viewed MR page
3. Viewed Security page on pipeline
4. Viewed Security Dashboard
5. GraphQL queries to verify new enum entry works.

• 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