Schemas specify scan type

What does this MR do?

This MR cleans up the issues associated with scan.type:

• Adds the missing secret_detection type to the Secrets schema
• Adds the missing api_fuzzing type to the DAST schema
• Schemas define compatible scan.type values, for example, a report that conforms to the SAST schema must have a sast scan.type

This is related to the issue gitlab-org/gitlab#239118 (closed).

Availability and Testing

• Review and add/update tests for this feature/bug

Reviews

• groupcomposition analysis @fcatteau
• groupstatic analysis @theoretick
• groupdynamic analysis @craigmsmith
• ~"group::fuzz testing" @mikeeddington